Loans (Details 3) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2011
Summary of nonperforming loans
Total nonperforming TDRs	$ 40,861	$ 44,452	$ 41,811
Total loans	4,019,159	3,831,285	3,760,426
Commercial Loan Portfolio [Member]
Summary of nonperforming loans
Total nonperforming TDRs	21,303	19,440	20,395
Total loans	2,159,893	2,085,325	2,034,890
Consumer Loan Portfolio [Member]
Summary of nonperforming loans
Total nonperforming TDRs	19,558	25,012	21,416
Total loans	1,859,266	1,745,960	1,725,536
Nonperforming [Member]
Summary of nonperforming loans
Total nonaccrual loans	78,324	78,394	91,112
Total accruing loans contractually past due 90 days or more as to interest or principal payments	2,098	3,817	3,015
Total nonperforming TDRs	10,455	24,058	26,268
Total loans	90,877	106,269	120,395
Nonperforming [Member] | Commercial Loan Portfolio [Member]
Summary of nonperforming loans
Total nonperforming TDRs	6,553	14,675	16,457
Nonperforming [Member] | Consumer Loan Portfolio [Member]
Summary of nonperforming loans
Total nonperforming TDRs	3,902	9,383	9,811
Nonperforming [Member] | Commercial [Member]
Summary of nonperforming loans
Total nonaccrual loans	15,217	10,726	10,804
Total accruing loans contractually past due 90 days or more as to interest or principal payments	273	1,381	282
Nonperforming [Member] | Real estate commercial [Member]
Summary of nonperforming loans
Total nonaccrual loans	41,311	44,438	48,854
Total accruing loans contractually past due 90 days or more as to interest or principal payments	247	374	415
Nonperforming [Member] | Real estate construction and land development [Member]
Summary of nonperforming loans
Total nonaccrual loans	6,664	6,190	7,877
Total accruing loans contractually past due 90 days or more as to interest or principal payments	0	287	0
Nonperforming [Member] | Real estate residential [Member]
Summary of nonperforming loans
Total nonaccrual loans	11,307	12,573	17,544
Total accruing loans contractually past due 90 days or more as to interest or principal payments	431	752	974
Nonperforming [Member] | Consumer installment and home equity [Member]
Summary of nonperforming loans
Total nonaccrual loans	3,825	4,467	6,033
Total accruing loans contractually past due 90 days or more as to interest or principal payments	$ 1,147	$ 1,023	$ 1,344