LOANS AND ALLOWANCE FOR LOAN LOSSES (Details 7) (USD $) In Thousands, unless otherwise specified	3 Months Ended	6 Months Ended
Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Real Estate Construction and Development [Member]
Number of Contracts	3	0	3	0
Recorded Investment	$ 1,364	$ 0	$ 1,364	$ 0
One To Four Family Residential [Member]
Number of Contracts	16	12	28	22
Recorded Investment	$ 3,587	$ 2,868	$ 5,894	$ 5,605

Number of financing receivables that have been modified by troubled debt restructurings within the previous 12 months and for which there was a payment default.

No definition available.

Name:	fbspra_FinancingReceivableSubsequentDefaultNumberOfContracts
Namespace Prefix:	fbspra_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration