Bank subsidiary (Details 12) (USD $) In Thousands, unless otherwise specified	3 Months Ended	9 Months Ended
	Sep. 30, 2012 item	Sep. 30, 2012 item
Loan modifications determined to be troubled debt restructurings
Number of loan modified by extending maturity date		1
Troubled debt restructurings real estate loans
Loan modifications determined to be troubled debt restructurings
Number of contracts	14	65
Pre-modification outstanding recorded investment	$ 3,100	$ 13,106
Post-modification outstanding recorded investment	2,850	12,182
Minimum period of payment default of loans determined to be TDRs		90 days
Troubled debt restructurings that subsequently defaulted
Loan modifications determined to be troubled debt restructurings
Number of contracts		1
Recorded investment	488	488
Residential 1-4 family | Troubled debt restructurings real estate loans
Loan modifications determined to be troubled debt restructurings
Number of contracts	4	26
Pre-modification outstanding recorded investment	1,415	5,884
Post-modification outstanding recorded investment	1,332	5,614
Residential land | Troubled debt restructurings real estate loans
Loan modifications determined to be troubled debt restructurings
Number of contracts	6	21
Pre-modification outstanding recorded investment	1,168	4,676
Post-modification outstanding recorded investment	1,001	4,022
Commercial loans | Troubled debt restructurings real estate loans
Loan modifications determined to be troubled debt restructurings
Number of contracts	4	18
Pre-modification outstanding recorded investment	517	2,546
Post-modification outstanding recorded investment	517	2,546
Commercial loans | Troubled debt restructurings that subsequently defaulted
Loan modifications determined to be troubled debt restructurings
Number of contracts		1
Recorded investment	$ 488	$ 488