Loans (Summary of Nonperforming Loans) (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012
Summary of nonperforming loans
Total nonperforming TDRs	$ 52,944	$ 48,566	$ 40,861
Total loans	4,522,671	4,167,735	4,019,159
Number of minimum days for performing and nonperforming trouble debt restructuring	90 days
Commercial Loan Portfolio [Member]
Summary of nonperforming loans
Total nonperforming TDRs	35,213	29,665	21,303
Total loans	2,445,787	2,264,820	2,159,893
Consumer Loan Portfolio [Member]
Summary of nonperforming loans
Total nonperforming TDRs	17,731	18,901	19,558
Total loans	2,076,884	1,902,915	1,859,266
Nonperforming [Member]
Summary of nonperforming loans
Total nonaccrual loans	55,286	71,298	78,324
Total accruing loans contractually past due 90 days or more as to interest or principal payments	1,659	2,359	2,098
Total nonperforming TDRs	18,873	17,197	10,455
Total loans	75,818	90,854	90,877
Nonperforming [Member] | Commercial Loan Portfolio [Member]
Summary of nonperforming loans
Total nonperforming TDRs	15,744	13,876	6,553
Nonperforming [Member] | Consumer Loan Portfolio [Member]
Summary of nonperforming loans
Total nonperforming TDRs	3,129	3,321	3,902
Nonperforming [Member] | Commercial [Member]
Summary of nonperforming loans
Total nonaccrual loans	11,809	14,601	15,217
Total accruing loans contractually past due 90 days or more as to interest or principal payments	281	0	273
Nonperforming [Member] | Real estate commercial [Member]
Summary of nonperforming loans
Total nonaccrual loans	28,623	37,660	41,311
Total accruing loans contractually past due 90 days or more as to interest or principal payments	0	87	247
Nonperforming [Member] | Real Estate Construction Loans [Member]
Summary of nonperforming loans
Total nonaccrual loans	183	1,217	933
Total accruing loans contractually past due 90 days or more as to interest or principal payments	0	0	0
Nonperforming [Member] | Land Development Loans [Member]
Summary of nonperforming loans
Total nonaccrual loans	2,954	4,184	5,731
Total accruing loans contractually past due 90 days or more as to interest or principal payments	0	0	0
Nonperforming [Member] | Real estate residential [Member]
Summary of nonperforming loans
Total nonaccrual loans	8,029	10,164	11,307
Total accruing loans contractually past due 90 days or more as to interest or principal payments	692	1,503	431
Nonperforming [Member] | Consumer Installment Loans [Member]
Summary of nonperforming loans
Total nonaccrual loans	665	739	876
Total accruing loans contractually past due 90 days or more as to interest or principal payments	0	0	0
Nonperforming [Member] | Home Equity Loans [Member]
Summary of nonperforming loans
Total nonaccrual loans	3,023	2,733	2,949
Total accruing loans contractually past due 90 days or more as to interest or principal payments	$ 686	$ 769	$ 1,147