Performance Management - Institutional Realty Shares	Dec. 31, 2025
Prospectus [Line Items]
Bar Chart and Performance Table [Heading]	<span style="color:#000000;font-family:Times New Roman;font-size:10.02pt;font-weight:bold;text-transform:uppercase;">Fund Performance</span>
Performance Narrative [Text Block]	The following bar chart and table provide some indication of the risks of investing in the Fund. The bar chart shows changes in the Fund’s performance from year to year. The table shows how the Fund’s average annual returns compare with the performance of a selected broad-based market index, the S&P 500 Index, over various time periods. The S&P 500 Index is an unmanaged index of common stocks that is frequently used as a general measure of U.S. stock market performance.In addition to the broad-based market index, the table shows performance of a linked benchmark (the “Linked Benchmark”). The Linked Benchmark is represented by the performance of the FTSE Nareit Equity REITs Index through March 31, 2019 and the FTSE Nareit All Equity REITs Index thereafter. The FTSE Nareit Equity REITs Index contains all tax-qualified real estate investment trusts (REITs) except timber and infrastructure REITs with more than 50% of total assets in qualifying real estate assets other than mortgages secured by real property that also meet minimum size and liquidity criteria. The FTSE Nareit All Equity REITs Index contains all tax-qualified REITs with more than 50% of total assets in qualifying real estate assets other than mortgages secured by real property that also meet minimum size and liquidity criteria. The Advisor believes that this index, as compared to the broad-based market index, is comprised of securities that are more representative of the Fund’s investment strategy.Past performance (both before and after taxes) is not, however, an indication as to how the Fund may perform in the future. Updated performance information, including the Fund’s NAV per share, is available at www.cohenandsteers.com or by calling (800) 330-7348.
Performance Past Does Not Indicate Future [Text]	<span style="color:#000000;font-family:Times New Roman;font-size:11.02pt;">Past </span><span style="color:#000000;font-family:Times New Roman;font-size:11.02pt;">performance (both before and after taxes) is not, however, an indication as to how the Fund may perform in the future.</span>
Performance Information Illustrates Variability of Returns [Text]	<span style="color:#000000;font-family:Times New Roman;font-size:11.02pt;">The following bar chart and table provide some indication of the risks of investing in the Fund. The bar chart shows changes in the Fund’s performance from year to year. The table shows how the Fund’s average annual returns compare with the performance of a selected broad-based market index, the S&P 500 Index, over various time periods. The S&P 500 Index is an unmanaged index of common stocks that is frequently used as a general measure of U.S. stock market performance.</span>
Performance Additional Market Index [Text]	<span style="color:#000000;font-family:Times New Roman;font-size:11.02pt;">In addition to the </span><span style="color:#000000;font-family:Times New Roman;font-size:11.02pt;">broad-based market index, the table shows performance of a linked benchmark (the “Linked Benchmark”). The Linked Benchmark is represented by the performance of the FTSE Nareit Equity REITs Index through March 31, 2019 and the FTSE Nareit All Equity REITs Index thereafter. The FTSE Nareit Equity REITs Index contains all tax-qualified real estate investment trusts (REITs) except timber and infrastructure REITs with more than 50% of total assets in qualifying real estate assets other than mortgages secured by real property that also meet minimum size and liquidity criteria. The FTSE Nareit All Equity REITs Index contains all tax-qualified REITs with more than 50% of total assets in qualifying real estate assets other than mortgages secured by real property that also meet minimum size and liquidity criteria. The Advisor believes that this index, as compared to the broad-based market index, is comprised of securities that are more representative of the Fund’s investment strategy.</span>
Bar Chart [Heading]	<span style="color:#000000;font-family:Times New Roman;font-size:11.2pt;font-weight:bold;">Cohen & Steers Institutional Realty Shares, Inc.</span> <br/><span style="color:#000000;font-family:Times New Roman;font-size:11.2pt;font-weight:bold;">Annual Total Returns</span>
Bar Chart Closing [Text Block]	Highest quarterly return during this period:17.15%quarter endedMarch 31, 2019Lowest quarterly return during this period:-22.80%quarter endedMarch 31, 2020
Performance Table Heading	<span style="color:#000000;font-family:Times New Roman;font-size:11.2pt;font-weight:bold;">Average Annual Total Returns </span><span style="font-family:Times New Roman;font-size:8.02pt;">(for the periods ended December 31, 2025)</span>
Performance Table Narrative	After-tax returns are calculated using the historical highest individual federal marginal income tax rates, and do not reflect the impact of state and local taxes. Actual after-tax returns depend on the investor’s tax situation and may differ from those shown, and the after-tax returns shown are not relevant to investors who hold their shares through tax-advantaged arrangements such as 401(k) plans or individual retirement accounts.
Performance Table Uses Highest Federal Rate	<span style="color:#000000;font-family:Times New Roman;font-size:11.02pt;">After-tax returns are calculated using the historical highest individual federal marginal income tax rates, and do not reflect the impact of state and local taxes.</span>
Performance Table Not Relevant to Tax Deferred	<span style="color:#000000;font-family:Times New Roman;font-size:11.02pt;"> Actual after-tax returns depend on the </span><span style="color:#000000;font-family:Times New Roman;font-size:11.02pt;">investor’s tax situation and may differ from those shown, and the after-tax returns shown are not relevant to investors who hold their shares through tax-advantaged arrangements such as 401(k) plans or individual retirement accounts.</span>
Performance Availability Website Address [Text]	<span style="color:#000000;font-family:Times New Roman;font-size:11.02pt;">www.cohenandsteers.com</span>
Performance Availability Phone [Text]	<span style="color:#000000;font-family:Times New Roman;font-size:11.02pt;">(800) 330-7348</span>
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Prospectus [Line Items]
Highest Quarterly Return, Label [Optional Text]	<span style="color:#000000;font-family:Times New Roman;font-size:11.02pt;margin-left:0.0pt;">Highest quarterly return during this period:</span>
Highest Quarterly Return	17.15%
Highest Quarterly Return, Date	Mar. 31, 2019
Lowest Quarterly Return, Label [Optional Text]	<span style="color:#000000;font-family:Times New Roman;font-size:11.02pt;margin-left:0.0pt;">Lowest quarterly return during this period:</span>
Lowest Quarterly Return	(22.80%)
Lowest Quarterly Return, Date	Mar. 31, 2020

Performance Management - Institutional Realty Shares

Dec. 31, 2025

Bar Chart and Performance Table [Heading]

Fund Performance

Performance Narrative [Text Block]

The following bar chart and table provide some indication of the risks of investing in the Fund. The bar chart shows changes in the Fund’s performance from year to year. The table shows how the Fund’s average annual returns compare with the performance of a selected broad-based market index, the S&P 500 Index, over various time periods. The S&P 500 Index is an unmanaged index of common stocks that is frequently used as a general measure of U.S. stock market performance.In addition to the broad-based market index, the table shows performance of a linked benchmark (the “Linked Benchmark”). The Linked Benchmark is represented by the performance of the FTSE Nareit Equity REITs Index through March 31, 2019 and the FTSE Nareit All Equity REITs Index thereafter. The FTSE Nareit Equity REITs Index contains all tax-qualified real estate investment trusts (REITs) except timber and infrastructure REITs with more than 50% of total assets in qualifying real estate assets other than mortgages secured by real property that also meet minimum size and liquidity criteria. The FTSE Nareit All Equity REITs Index contains all tax-qualified REITs with more than 50% of total assets in qualifying real estate assets other than mortgages secured by real property that also meet minimum size and liquidity criteria. The Advisor believes that this index, as compared to the broad-based market index, is comprised of securities that are more representative of the Fund’s investment strategy.Past performance (both before and after taxes) is not, however, an indication as to how the Fund may perform in the future. Updated performance information, including the Fund’s NAV per share, is available at www.cohenandsteers.com or by calling (800) 330-7348.

Performance Past Does Not Indicate Future [Text]

Past performance (both before and after taxes) is not, however, an indication as to how the Fund may perform in the future.

Performance Information Illustrates Variability of Returns [Text]

The following bar chart and table provide some indication of the risks of investing in the Fund. The bar chart shows changes in the Fund’s performance from year to year. The table shows how the Fund’s average annual returns compare with the performance of a selected broad-based market index, the S&P 500 Index, over various time periods. The S&P 500 Index is an unmanaged index of common stocks that is frequently used as a general measure of U.S. stock market performance.

Performance Additional Market Index [Text]

In addition to the broad-based market index, the table shows performance of a linked benchmark (the “Linked Benchmark”). The Linked Benchmark is represented by the performance of the FTSE Nareit Equity REITs Index through March 31, 2019 and the FTSE Nareit All Equity REITs Index thereafter. The FTSE Nareit Equity REITs Index contains all tax-qualified real estate investment trusts (REITs) except timber and infrastructure REITs with more than 50% of total assets in qualifying real estate assets other than mortgages secured by real property that also meet minimum size and liquidity criteria. The FTSE Nareit All Equity REITs Index contains all tax-qualified REITs with more than 50% of total assets in qualifying real estate assets other than mortgages secured by real property that also meet minimum size and liquidity criteria. The Advisor believes that this index, as compared to the broad-based market index, is comprised of securities that are more representative of the Fund’s investment strategy.

Bar Chart [Heading]

Cohen & Steers Institutional Realty Shares, Inc. Annual Total Returns

Bar Chart Closing [Text Block]

Highest quarterly return during this period:17.15%quarter endedMarch 31, 2019Lowest quarterly return during this period:-22.80%quarter endedMarch 31, 2020

Performance Table Heading

Average Annual Total Returns (for the periods ended December 31, 2025)

Performance Table Narrative

After-tax returns are calculated using the historical highest individual federal marginal income tax rates, and do not reflect the impact of state and local taxes. Actual after-tax returns depend on the investor’s tax situation and may differ from those shown, and the after-tax returns shown are not relevant to investors who hold their shares through tax-advantaged arrangements such as 401(k) plans or individual retirement accounts.

Performance Table Uses Highest Federal Rate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates, and do not reflect the impact of state and local taxes.

Performance Table Not Relevant to Tax Deferred

Actual after-tax returns depend on the investor’s tax situation and may differ from those shown, and the after-tax returns shown are not relevant to investors who hold their shares through tax-advantaged arrangements such as 401(k) plans or individual retirement accounts.

Performance Availability Website Address [Text]

www.cohenandsteers.com

Performance Availability Phone [Text]

(800) 330-7348

Prospectus [Line Items]

Highest Quarterly Return, Label [Optional Text]

Highest quarterly return during this period:

Highest Quarterly Return

17.15%

Highest Quarterly Return, Date

Mar. 31, 2019

Lowest Quarterly Return, Label [Optional Text]

Lowest quarterly return during this period:

Lowest Quarterly Return

(22.80%)

Lowest Quarterly Return, Date

Mar. 31, 2020