Bank subsidiary (Details 13) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013 contract	Jun. 30, 2012 contract	Jun. 30, 2013 contract	Jun. 30, 2012 contract
Loan modifications determined to be troubled debt restructurings
Number of loan modified by extending maturity date				3
Commitments to borrowers whose loan terms are impaired or modified under troubled debt restructuring	$ 0		$ 0
Troubled debt restructurings real estate loans
Loan modifications determined to be troubled debt restructurings
Number of contracts	21	31	32	51
Pre-modification outstanding recorded investment	6,475	6,699	8,983	10,006
Post-modification outstanding recorded investment	6,652	6,321	8,798	9,332
Minimum period of payment default of loans determined to be TDRs			90 days	90 days
Troubled debt restructurings that subsequently defaulted
Loan modifications determined to be troubled debt restructurings
Number of contracts				3
Recorded investment		847		847
Residential 1-4 family | Troubled debt restructurings real estate loans
Loan modifications determined to be troubled debt restructurings
Number of contracts	14	15	18	22
Pre-modification outstanding recorded investment	4,645	3,056	5,767	4,469
Post-modification outstanding recorded investment	4,775	2,872	5,838	4,282
Home equity line of credit | Troubled debt restructurings real estate loans
Loan modifications determined to be troubled debt restructurings
Number of contracts			4
Pre-modification outstanding recorded investment			462
Post-modification outstanding recorded investment			215
Residential land | Troubled debt restructurings real estate loans
Loan modifications determined to be troubled debt restructurings
Number of contracts	4	8	7	15
Pre-modification outstanding recorded investment	1,116	1,774	2,040	3,508
Post-modification outstanding recorded investment	1,163	1,580	2,031	3,021
Commercial loans | Troubled debt restructurings real estate loans
Loan modifications determined to be troubled debt restructurings
Number of contracts	3	8	3	14
Pre-modification outstanding recorded investment	714	1,869	714	2,029
Post-modification outstanding recorded investment	714	1,869	714	2,029
Commercial loans | Troubled debt restructurings that subsequently defaulted
Loan modifications determined to be troubled debt restructurings
Number of contracts				3
Recorded investment		$ 847		$ 847