Bank subsidiary (Details 14) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011 loan
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	146
Pre-modification outstanding recorded investment	56,665
Post-modification outstanding recorded investment	55,266
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	5
Recorded investment	1,327
Residential 1-4 family | Troubled debt restructurings
Loan modifications determined to be troubled debt restructurings
Number of contracts	42
Pre-modification outstanding recorded investment	11,233
Post-modification outstanding recorded investment	9,853
Home equity line of credit | Troubled debt restructurings
Loan modifications determined to be troubled debt restructurings
Number of contracts	1
Pre-modification outstanding recorded investment	93
Post-modification outstanding recorded investment	93
Residential land | Troubled debt restructurings
Loan modifications determined to be troubled debt restructurings
Number of contracts	46
Pre-modification outstanding recorded investment	9,965
Post-modification outstanding recorded investment	9,946
Residential land | Troubled debt restructurings that subsequently defaulted
Loan modifications determined to be troubled debt restructurings
Number of contracts	1
Recorded investment	528
Commercial loans | Troubled debt restructurings
Loan modifications determined to be troubled debt restructurings
Number of contracts	56
Pre-modification outstanding recorded investment	35,349
Post-modification outstanding recorded investment	35,349
Commercial loans | Troubled debt restructurings that subsequently defaulted
Loan modifications determined to be troubled debt restructurings
Number of contracts	4
Recorded investment	799
Consumer loans | Troubled debt restructurings
Loan modifications determined to be troubled debt restructurings
Number of contracts	1
Pre-modification outstanding recorded investment	25
Post-modification outstanding recorded investment	25