Bank subsidiary (Details 9) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Credit risk profile based on payment activity for loans
30-59 days past due	$ 11,506	$ 14,016
60-89 days past due	3,436	5,120
Greater than 90 days	44,946	41,433
Total past due	59,888	60,569
Current	3,795,947	3,730,287
Total financing receivables	3,855,835	3,790,856
Recorded Investment greater than 90 days and accruing	1,628	373
Residential 1-4 family
Credit risk profile based on payment activity for loans
30-59 days past due	5,435	6,353
60-89 days past due	1,277	1,741
Greater than 90 days	23,292	24,054
Total past due	30,004	32,148
Current	1,885,203	1,834,302
Total financing receivables	1,915,207	1,866,450
Commercial real estate
Credit risk profile based on payment activity for loans
30-59 days past due	743	85
Greater than 90 days	3,811	6,750
Total past due	4,554	6,835
Current	387,125	368,842
Total financing receivables	391,679	375,677
Home equity line of credit
Credit risk profile based on payment activity for loans
30-59 days past due	649	1,077
60-89 days past due	371	142
Greater than 90 days	1,323	1,319
Total past due	2,343	2,538
Current	646,561	627,637
Total financing receivables	648,904	630,175
Residential land
Credit risk profile based on payment activity for loans
30-59 days past due	599	2,851
60-89 days past due	1,138	75
Greater than 90 days	9,748	7,788
Total past due	11,485	10,714
Current	12,409	15,101
Total financing receivables	23,894	25,815
Recorded Investment greater than 90 days and accruing	1,268
Commercial construction
Credit risk profile based on payment activity for loans
Current	40,698	43,988
Total financing receivables	40,698	43,988
Residential construction
Credit risk profile based on payment activity for loans
Current	8,275	6,171
Total financing receivables	8,275	6,171
Commercial loans
Credit risk profile based on payment activity for loans
30-59 days past due	3,513	3,052
60-89 days past due	400	2,814
Greater than 90 days	6,370	1,098
Total past due	10,283	6,964
Current	689,635	714,385
Total financing receivables	699,918	721,349
Recorded Investment greater than 90 days and accruing	88	131
Consumer loans
Credit risk profile based on payment activity for loans
30-59 days past due	567	598
60-89 days past due	250	348
Greater than 90 days	402	424
Total past due	1,219	1,370
Current	126,041	119,861
Total financing receivables	127,260	121,231
Recorded Investment greater than 90 days and accruing	$ 272	$ 242