S000006330 [Member] Average Annual Total Returns |
12 Months Ended | 58 Months Ended | 60 Months Ended | 120 Months Ended | 310 Months Ended | 378 Months Ended | ||
|---|---|---|---|---|---|---|---|---|
Dec. 31, 2024 |
Dec. 31, 2024 |
Dec. 31, 2024 |
Dec. 31, 2024 |
Dec. 31, 2024 |
Dec. 31, 2024 |
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| Bloomberg U.S. Aggregate Bond Index (reflects no deduction for fees, expenses or taxes) | ||||||||
| Prospectus [Line Items] | ||||||||
| Average Annual Return, Percent | [1] | 1.25% | 4.34% | (0.33%) | 1.35% | |||
| I Class | ||||||||
| Prospectus [Line Items] | ||||||||
| Average Annual Return, Percent | 1.82% | (0.89%) | 0.93% | 5.09% | ||||
| Performance Inception Date | Jun. 17, 1993 | |||||||
| I Class | After Taxes on Distributions | ||||||||
| Prospectus [Line Items] | ||||||||
| Average Annual Return, Percent | (0.79%) | (2.55%) | (0.63%) | 2.86% | ||||
| Performance Inception Date | Jun. 17, 1993 | |||||||
| I Class | After Taxes on Distributions and Sales | ||||||||
| Prospectus [Line Items] | ||||||||
| Average Annual Return, Percent | 1.06% | (1.33%) | 0.07% | 3.03% | ||||
| Performance Inception Date | Jun. 17, 1993 | |||||||
| N Class | ||||||||
| Prospectus [Line Items] | ||||||||
| Average Annual Return, Percent | 1.62% | (1.09%) | 0.68% | 4.35% | ||||
| Performance Inception Date | Mar. 01, 1999 | |||||||
| Plan Class | ||||||||
| Prospectus [Line Items] | ||||||||
| Average Annual Return, Percent | 1.77% | (1.74%) | ||||||
| Performance Inception Date | Feb. 28, 2020 | |||||||
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