Bank subsidiary (Details 8) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Credit risk profile based on payment activity for loans
30-59 days past due	$ 10,319	$ 15,193
60-89 days past due	6,109	6,729
Greater than 90 days	43,343	44,397
Total past due	59,771	66,319
Current	3,698,132	3,628,216
Total financing receivables	3,757,903	3,694,535
Recorded Investment greater than 90 days and accruing	2,956	541
Residential 1-4 family
Credit risk profile based on payment activity for loans
30-59 days past due	5,830	10,391
60-89 days past due	1,727	4,583
Greater than 90 days	28,626	28,113
Total past due	36,183	43,087
Current	1,863,397	1,883,687
Total financing receivables	1,899,580	1,926,774
Commercial real estate
Credit risk profile based on payment activity for loans
Greater than 90 days	2,929
Total past due	2,929
Current	364,836	331,931
Total financing receivables	367,765	331,931
Home equity line of credit
Credit risk profile based on payment activity for loans
30-59 days past due	584	1,671
60-89 days past due	758	494
Greater than 90 days	1,965	1,421
Total past due	3,307	3,586
Current	600,972	531,895
Total financing receivables	604,279	535,481
Residential land
Credit risk profile based on payment activity for loans
30-59 days past due	1,346	2,352
60-89 days past due	3,017	575
Greater than 90 days	6,384	13,037
Total past due	10,747	15,964
Current	18,533	29,428
Total financing receivables	29,280	45,392
Recorded Investment greater than 90 days and accruing	2,473	205
Commercial construction
Credit risk profile based on payment activity for loans
Current	42,913	41,950
Total financing receivables	42,913	41,950
Residential construction
Credit risk profile based on payment activity for loans
Current	5,648	3,327
Total financing receivables	5,648	3,327
Commercial loans
Credit risk profile based on payment activity for loans
30-59 days past due	1,681	226
60-89 days past due	251	733
Greater than 90 days	2,948	1,340
Total past due	4,880	2,299
Current	699,220	714,128
Total financing receivables	704,100	716,427
Recorded Investment greater than 90 days and accruing	123	28
Consumer loans
Credit risk profile based on payment activity for loans
30-59 days past due	878	553
60-89 days past due	356	344
Greater than 90 days	491	486
Total past due	1,725	1,383
Current	102,613	91,870
Total financing receivables	104,338	93,253
Recorded Investment greater than 90 days and accruing	$ 360	$ 308