Bank subsidiary (Details 12) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012 contract D	Mar. 31, 2011 contract
Loan modifications determined to be troubled debt restructurings
Number of loans modified by extending maturity date	4
Troubled debt restructurings
Loan modifications determined to be troubled debt restructurings
Number of contracts	20	47
Pre-modification outstanding recorded investment	$ 3,307	$ 15,370
Post-modification outstanding recorded investment	3,011	15,255
Minimum period of payment default of loans determined to be TDRs (in days)	90
Troubled debt restructurings that subsequently defaulted
Loan modifications determined to be troubled debt restructurings
Number of contracts	4	7
Recorded investment	879	1,093
Residential 1-4 family | Troubled debt restructurings
Loan modifications determined to be troubled debt restructurings
Number of contracts	7	9
Pre-modification outstanding recorded investment	1,413	2,358
Post-modification outstanding recorded investment	1,410	2,235
Residential land | Troubled debt restructurings
Loan modifications determined to be troubled debt restructurings
Number of contracts	7	18
Pre-modification outstanding recorded investment	1,734	2,912
Post-modification outstanding recorded investment	1,441	2,920
Residential land | Troubled debt restructurings that subsequently defaulted
Loan modifications determined to be troubled debt restructurings
Number of contracts		1
Recorded investment		396
Commercial loans | Troubled debt restructurings
Loan modifications determined to be troubled debt restructurings
Number of contracts	6	20
Pre-modification outstanding recorded investment	160	10,100
Post-modification outstanding recorded investment	160	10,100
Commercial loans | Troubled debt restructurings that subsequently defaulted
Loan modifications determined to be troubled debt restructurings
Number of contracts	4	6
Recorded investment	$ 879	$ 697