Bank subsidiary (Details 7) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Allowance for loan losses:
Valuation allowance, balance at the beginning of the period	$ 40,116	$ 41,985
Charge-offs	(957)	(2,178)
Recoveries	769	1,065
Provision	995	1,858
Valuation allowance, balance at the end of the period	40,923	42,730
Valuation allowance, balance at the end of the period	40,923	42,730
Ending balance: individually evaluated for impairment	5,685	7,851
Ending balance: collectively evaluated for impairment	35,238	34,879
Financing Receivables:
Total financing receivables	4,196,369	3,855,835	4,158,953
Ending balance: individually evaluated for impairment	55,631	74,182
Ending balance: collectively evaluated for impairment	4,140,738	3,781,653
Residential 1-4 family
Allowance for loan losses:
Valuation allowance, balance at the beginning of the period	5,534	6,068
Charge-offs	(266)	(210)
Recoveries	341	192
Provision	(134)	(39)
Valuation allowance, balance at the end of the period	5,475	6,011
Valuation allowance, balance at the end of the period	5,475	6,011
Ending balance: individually evaluated for impairment	906	454
Ending balance: collectively evaluated for impairment	4,569	5,557
Financing Receivables:
Total financing receivables	1,985,812	1,915,207	2,006,007
Ending balance: individually evaluated for impairment	20,141	25,320
Ending balance: collectively evaluated for impairment	1,965,671	1,889,887
Commercial real estate
Allowance for loan losses:
Valuation allowance, balance at the beginning of the period	5,059	2,965
Provision	656	3,691
Valuation allowance, balance at the end of the period	5,715	6,656
Valuation allowance, balance at the end of the period	5,715	6,656
Ending balance: individually evaluated for impairment	1,544	3,169
Ending balance: collectively evaluated for impairment	4,171	3,487
Financing Receivables:
Total financing receivables	452,303	391,679	440,443
Ending balance: individually evaluated for impairment	4,558	10,662
Ending balance: collectively evaluated for impairment	447,745	381,017
Home equity line of credit
Allowance for loan losses:
Valuation allowance, balance at the beginning of the period	5,229	4,493
Charge-offs	0	(670)
Recoveries	11	194
Provision	729	540
Valuation allowance, balance at the end of the period	5,969	4,557
Valuation allowance, balance at the end of the period	5,969	4,557
Ending balance: individually evaluated for impairment		0
Ending balance: collectively evaluated for impairment	5,969	4,557
Financing Receivables:
Total financing receivables	764,483	648,904	739,331
Ending balance: individually evaluated for impairment	1,164	1,259
Ending balance: collectively evaluated for impairment	763,319	647,645
Residential land
Allowance for loan losses:
Valuation allowance, balance at the beginning of the period	1,817	4,275
Charge-offs	(6)	(227)
Recoveries	86	137
Provision	(322)	(1,442)
Valuation allowance, balance at the end of the period	1,575	2,743
Valuation allowance, balance at the end of the period	1,575	2,743
Ending balance: individually evaluated for impairment	1,102	1,943
Ending balance: collectively evaluated for impairment	473	800
Financing Receivables:
Total financing receivables	15,906	23,894	16,176
Ending balance: individually evaluated for impairment	10,351	17,618
Ending balance: collectively evaluated for impairment	5,555	6,276
Commercial construction
Allowance for loan losses:
Valuation allowance, balance at the beginning of the period	2,397	2,023
Provision	666	(151)
Valuation allowance, balance at the end of the period	3,063	1,872
Valuation allowance, balance at the end of the period	3,063	1,872
Ending balance: collectively evaluated for impairment	3,063	1,872
Financing Receivables:
Total financing receivables	66,578	40,698	52,112
Ending balance: collectively evaluated for impairment	66,578	40,698
Residential construction
Allowance for loan losses:
Valuation allowance, balance at the beginning of the period	19	9
Provision	5	3
Valuation allowance, balance at the end of the period	24	12
Valuation allowance, balance at the end of the period	24	12
Ending balance: collectively evaluated for impairment	24	12
Financing Receivables:
Total financing receivables	16,474	8,275	12,774
Ending balance: collectively evaluated for impairment	16,474	8,275
Commercial loans
Allowance for loan losses:
Valuation allowance, balance at the beginning of the period	15,803	15,931
Charge-offs	(124)	(426)
Recoveries	100	392
Provision	(187)	(934)
Valuation allowance, balance at the end of the period	15,592	14,963
Valuation allowance, balance at the end of the period	15,592	14,963
Ending balance: individually evaluated for impairment	2,133	2,285
Ending balance: collectively evaluated for impairment	13,459	12,678
Financing Receivables:
Total financing receivables	786,611	699,918	783,388
Ending balance: individually evaluated for impairment	19,399	19,302
Ending balance: collectively evaluated for impairment	767,212	680,616
Consumer loans
Allowance for loan losses:
Valuation allowance, balance at the beginning of the period	2,367	4,019
Charge-offs	(561)	(645)
Recoveries	231	150
Provision	279	131
Valuation allowance, balance at the end of the period	2,316	3,655
Valuation allowance, balance at the end of the period	2,316	3,655
Ending balance: collectively evaluated for impairment	2,316	3,655
Financing Receivables:
Total financing receivables	108,202	127,260	108,722
Ending balance: individually evaluated for impairment	18	21
Ending balance: collectively evaluated for impairment	108,184	127,239
Unallocated
Allowance for loan losses:
Valuation allowance, balance at the beginning of the period	1,891	2,202
Provision	(697)	59
Valuation allowance, balance at the end of the period	1,194	2,261
Valuation allowance, balance at the end of the period	1,194	2,261
Ending balance: collectively evaluated for impairment	$ 1,194	$ 2,261