Weighted average amortization period of finite-lived intangible assets acquired either individually or as part of a group of assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (a)(3)
-URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16265-109275

+ Details

Name:	us-gaap_AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_BusinessAcquisitionLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

For contingent consideration arrangements recognized in connection with a business combination, this element represents an estimate of the high-end of the potential range (undiscounted) of the consideration which may be paid.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (c)(3)
-URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e6927-128479

+ Details

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

- Definition

Cash outflow representing an adjustment to the purchase price of a previous acquisition.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3213-108585

+ Details

Name:	us-gaap_PaymentsForPreviousAcquisition
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	us-gaap_BusinessAcquisitionAxis=br_ClearStructureMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessAcquisitionAxis=br_RockallTechnologiesLimitedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessAcquisitionAxis=br_RPMMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=br_SoftwareTechnologyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessAcquisitionAxis=br_ShadowFinancialServicesIncMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessAcquisitionAxis=br_Fi360Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=us-gaap_CustomerRelationshipsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessAcquisitionAxis=br_TDAmeritradeTrustCompanyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Acquisitions - Additional Information (Details) - USD ($) $ in Millions	1 Months Ended				3 Months Ended
	Nov. 30, 2019	Oct. 31, 2019	Jun. 30, 2019	May 31, 2019	Sep. 30, 2019
Clear-Structure
Business Acquisition [Line Items]
Potential maximum pay-out	$ 12.5
Rockall
Business Acquisition [Line Items]
Potential maximum pay-out				$ 10.1
Payments for previous acquisition					$ 0.5
RPM
Business Acquisition [Line Items]
Potential maximum pay-out			$ 3.7
Payments for previous acquisition					$ 40.9
Software Technology \| Shadow Financial
Business Acquisition [Line Items]
Useful life of intangible assets acquired		5 years
Software Technology \| Fi360
Business Acquisition [Line Items]
Useful life of intangible assets acquired	5 years
Software Technology \| Rockall
Business Acquisition [Line Items]
Useful life of intangible assets acquired				4 years
Software Technology \| RPM
Business Acquisition [Line Items]
Useful life of intangible assets acquired			5 years
Customer Relationships \| Shadow Financial
Business Acquisition [Line Items]
Useful life of intangible assets acquired		7 years
Customer Relationships \| Fi360
Business Acquisition [Line Items]
Useful life of intangible assets acquired	7 years
Customer Relationships \| Rockall
Business Acquisition [Line Items]
Useful life of intangible assets acquired				6 years
Customer Relationships \| RPM
Business Acquisition [Line Items]
Useful life of intangible assets acquired			7 years
Customer Relationships \| TD Ameritrade*
Business Acquisition [Line Items]
Useful life of intangible assets acquired			7 years