Name:	bsf_BusinessAcquisitionsProFormaNetInterestIncome
Namespace Prefix:	bsf_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

The pro forma non interest income for the period as if the business combination or combinations had been completed at the beginning of a period.

No definition available.

Name:	bsf_BusinessAcquisitionsProFormaNoninterestIncome
Namespace Prefix:	bsf_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	bsf_Note2AcquisitionDetailsProFormaInformationLineItems
Namespace Prefix:	bsf_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

The pro forma basic net income per share for a period as if the business combination or combinations had been completed at the beginning of a period.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (h)(2)-(3)

-URI http://asc.fasb.org/extlink&oid=25497992&loc=d3e1392-128463

Name:	us-gaap_BusinessAcquisitionProFormaEarningsPerShareBasic
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

The pro forma diluted net income per share for a period as if the business combination or combinations had been completed at the beginning of a period.

Name:	us-gaap_BusinessAcquisitionProFormaEarningsPerShareDiluted
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

The pro forma net Income or Loss for the period as if the business combination or combinations had been completed at the beginning of a period.