Bank subsidiary (Details 7) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2008
Allowance for loan losses:
Valuation allowance, balance at the beginning of the period	$ 40,646	$ 41,679	$ 35,798
Charge-offs	(19,490)	(24,815)
Recoveries	1,741	2,888
Provision	15,009	20,894
Valuation allowance, balance at the end of the period	37,906	40,646	35,798
Ending balance: individually evaluated for impairment	3,704	3,460
Ending balance: collectively evaluated for impairment	34,202	37,186
Financing Receivables:
Ending balance	3,694,535	3,546,056
Ending balance: individually evaluated for impairment	128,488	116,191
Ending balance: collectively evaluated for impairment	3,566,047	3,429,865
Residential 1-4 family
Allowance for loan losses:
Valuation allowance, balance at the beginning of the period	6,497	5,522
Charge-offs	(5,528)	(6,142)
Recoveries	110	744
Provision	5,421	6,373
Valuation allowance, balance at the end of the period	6,500	6,497
Ending balance: individually evaluated for impairment	203	230
Ending balance: collectively evaluated for impairment	6,297	6,267
Financing Receivables:
Ending balance	1,926,774	2,087,813
Ending balance: individually evaluated for impairment	26,012	34,615
Ending balance: collectively evaluated for impairment	1,900,762	2,053,198
Commercial real estate
Allowance for loan losses:
Valuation allowance, balance at the beginning of the period	1,474	861
Provision	214	613
Valuation allowance, balance at the end of the period	1,688	1,474
Ending balance: collectively evaluated for impairment	1,688	1,474
Financing Receivables:
Ending balance	331,931	300,689
Ending balance: individually evaluated for impairment	13,397	12,156
Ending balance: collectively evaluated for impairment	318,534	288,533
Home equity line of credit
Allowance for loan losses:
Valuation allowance, balance at the beginning of the period	4,269	4,679
Charge-offs	(1,439)	(2,517)
Recoveries	25	63
Provision	1,499	2,044
Valuation allowance, balance at the end of the period	4,354	4,269
Ending balance: collectively evaluated for impairment	4,354	4,269
Financing Receivables:
Ending balance	535,481	416,453
Ending balance: individually evaluated for impairment	1,450	827
Ending balance: collectively evaluated for impairment	534,031	415,626
Residential land
Allowance for loan losses:
Valuation allowance, balance at the beginning of the period	6,411	4,252
Charge-offs	(4,071)	(6,487)
Recoveries	170	63
Provision	1,285	8,583
Valuation allowance, balance at the end of the period	3,795	6,411
Ending balance: individually evaluated for impairment	2,525	1,642
Ending balance: collectively evaluated for impairment	1,270	4,769
Financing Receivables:
Ending balance	45,392	65,599
Ending balance: individually evaluated for impairment	39,364	39,631
Ending balance: collectively evaluated for impairment	6,028	25,968
Commercial construction
Allowance for loan losses:
Valuation allowance, balance at the beginning of the period	1,714	3,068
Provision	174	(1,354)
Valuation allowance, balance at the end of the period	1,888	1,714
Ending balance: collectively evaluated for impairment	1,888	1,714
Financing Receivables:
Ending balance	41,950	38,079
Ending balance: collectively evaluated for impairment	41,950	38,079
Residential construction
Allowance for loan losses:
Valuation allowance, balance at the beginning of the period	7	19
Provision	(3)	(12)
Valuation allowance, balance at the end of the period	4	7
Ending balance: collectively evaluated for impairment	4	7
Financing Receivables:
Ending balance	3,327	5,602
Ending balance: collectively evaluated for impairment	3,327	5,602
Commercial loans
Allowance for loan losses:
Valuation allowance, balance at the beginning of the period	16,015	19,498
Charge-offs	(5,335)	(6,261)
Recoveries	869	1,537
Provision	3,318	1,241
Valuation allowance, balance at the end of the period	14,867	16,015
Ending balance: individually evaluated for impairment	976	1,588
Ending balance: collectively evaluated for impairment	13,891	14,427
Financing Receivables:
Ending balance	716,427	551,683
Ending balance: individually evaluated for impairment	48,241	28,886
Ending balance: collectively evaluated for impairment	668,186	522,797
Consumer loans
Allowance for loan losses:
Valuation allowance, balance at the beginning of the period	3,325	2,590
Charge-offs	(3,117)	(3,408)
Recoveries	567	481
Provision	3,031	3,662
Valuation allowance, balance at the end of the period	3,806	3,325
Ending balance: collectively evaluated for impairment	3,806	3,325
Financing Receivables:
Ending balance	93,253	80,138
Ending balance: individually evaluated for impairment	24	76
Ending balance: collectively evaluated for impairment	93,229	80,062
Unallocated
Allowance for loan losses:
Valuation allowance, balance at the beginning of the period	934	1,190
Provision	70	(256)
Valuation allowance, balance at the end of the period	1,004	934
Ending balance: collectively evaluated for impairment	$ 1,004	$ 934