Contractual Commitments, Contingencies, and Off-Balance Sheet Arrangements - Data Center Agreements - Capitalized Costs (Details) $ in Millions	12 Months Ended
Jun. 30, 2024 USD ($)
Data Center Agreements
Capitalized Contract Cost [Roll Forward]
Capitalized costs, beginning balance	$ 70.7
Capitalized costs incurred	0.0
Impact of foreign currency exchange	0.0
Total capitalized costs, ending balance	70.7
Total accumulated amortization	(59.3)
Net Deferred Costs	11.4
Amended and Restated IT Services Agreement
Capitalized Contract Cost [Roll Forward]
Capitalized costs, beginning balance	63.0
Capitalized costs incurred	0.0
Impact of foreign currency exchange	0.0
Total capitalized costs, ending balance	63.0
Total accumulated amortization	(53.2)
Net Deferred Costs	9.8
Other
Capitalized Contract Cost [Roll Forward]
Capitalized costs, beginning balance	7.7
Capitalized costs incurred	0.0
Impact of foreign currency exchange	0.0
Total capitalized costs, ending balance	7.7
Total accumulated amortization	(6.1)
Net Deferred Costs	$ 1.6

Capitalized Contract Cost, Costs Incurred

No definition available.

Name:	br_CapitalizedContractCostCostsIncurred
Namespace Prefix:	br_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Capitalized Contract Cost [Roll Forward]

+ References

No definition available.

+ Details

Name:	br_CapitalizedContractCostRollForward
Namespace Prefix:	br_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Capitalized Contract Costs, Foreign Currency Exchange Adjustment

+ References

No definition available.

+ Details

Name:	br_CapitalizedContractCostsForeignCurrencyExchangeAdjustment
Namespace Prefix:	br_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of accumulated amortization of asset recognized from cost incurred to obtain or fulfill contract with customer.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 340
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479483/340-40-50-3

+ Details

Name:	us-gaap_CapitalizedContractCostAccumulatedAmortization
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount, before accumulated amortization and accumulated impairment loss, of asset recognized from cost incurred to obtain or fulfill contract with customer.

+ References

+ Details

Name:	us-gaap_CapitalizedContractCostGross
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount, after accumulated amortization and accumulated impairment loss, of asset recognized from cost incurred to obtain or fulfill contract with customer.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 340
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479483/340-40-50-3

+ Details

Name:	us-gaap_CapitalizedContractCostNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_LongTermPurchaseCommitmentByCategoryOfItemPurchasedAxis=br_DataCenterAgreementsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongTermPurchaseCommitmentByCategoryOfItemPurchasedAxis=br_InformationTechnologyServicesAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongTermPurchaseCommitmentByCategoryOfItemPurchasedAxis=br_OtherDataCenterAgreementsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: