Name:	brkl_InterestExpenseDepositsExcludingBrokeredDeposits
Namespace Prefix:	brkl_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- References

No definition available.

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

Interest expense incurred on all money market deposits.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04.6)
-URI http://asc.fasb.org/extlink&oid=116637391&loc=SL114874048-224260

Name:	us-gaap_InterestExpenseMoneyMarketDeposits
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Interest expense incurred on the amount of Negotiable Order of Withdrawal (NOW). Interest-bearing transaction account that combines the payable on demand feature of checks and investment feature of savings accounts. A NOW account is functionally an interest paying checking account.

Name:	us-gaap_InterestExpenseNegotiableOrderOfWithdrawalNOWDeposits
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Interest expense incurred on all savings account deposits.

Name:	us-gaap_InterestExpenseSavingsDeposits
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

The aggregate interest expense incurred on time deposits, including certificates of deposits, in domestic offices.