Note 12 - Other Borrowings (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014
Disclosure Text Block [Abstract]
Federal Home Loan Bank Advances, Letter of Credit Disclosures, Maximum Amount Available	$ 25.0

Amount of maximum potential advances or credit available related to letters of credit from the Federal Home Loan Bank (FHLB).

No definition available.

Name:	bsf_FederalHomeLoanBankAdvancesLetterOfCreditDisclosuresMaximumAmountAvailable
Namespace Prefix:	bsf_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant