(Summary of nonperforming loans) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Summary of nonperforming loans
Total nonperforming TDRs	$ 48,566	$ 44,452
Total loans	4,167,735	3,831,285
Commercial Loan Portfolio [Member]
Summary of nonperforming loans
Total nonperforming TDRs	29,665	19,440
Total loans	2,264,820	2,085,325
Consumer Loan Portfolio [Member]
Summary of nonperforming loans
Total nonperforming TDRs	18,901	25,012
Total loans	1,902,915	1,745,960
Nonperforming [Member]
Summary of nonperforming loans
Total nonaccrual loans	71,298	78,394
Total accruing loans contractually past due 90 days or more as to interest or principal payments	2,359	3,817
Total nonperforming TDRs	17,197	24,058
Total loans	90,854	106,269
Nonperforming [Member] | Commercial Loan Portfolio [Member]
Summary of nonperforming loans
Total nonperforming TDRs	13,876	14,675
Nonperforming [Member] | Consumer Loan Portfolio [Member]
Summary of nonperforming loans
Total nonperforming TDRs	3,321	9,383
Nonperforming [Member] | Commercial [Member]
Summary of nonperforming loans
Total nonaccrual loans	14,601	10,726
Total accruing loans contractually past due 90 days or more as to interest or principal payments	0	1,381
Nonperforming [Member] | Real estate commercial [Member]
Summary of nonperforming loans
Total nonaccrual loans	37,660	44,438
Total accruing loans contractually past due 90 days or more as to interest or principal payments	87	374
Nonperforming [Member] | Real estate construction and land development [Member]
Summary of nonperforming loans
Total nonaccrual loans	5,401	6,190
Total accruing loans contractually past due 90 days or more as to interest or principal payments	0	287
Nonperforming [Member] | Real estate residential [Member]
Summary of nonperforming loans
Total nonaccrual loans	10,164	12,573
Total accruing loans contractually past due 90 days or more as to interest or principal payments	1,503	752
Nonperforming [Member] | Consumer installment and home equity [Member]
Summary of nonperforming loans
Total nonaccrual loans	3,472	4,467
Total accruing loans contractually past due 90 days or more as to interest or principal payments	$ 769	$ 1,023