Loans (Summary of Nonperforming Loans) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012
Summary of nonperforming loans
Total nonperforming TDRs	$ 49,638	$ 48,566	$ 43,926
Total loans	4,185,261	4,167,735	3,843,098
Number of minimum days for performing and nonperforming trouble debt restructuring	90 days
Commercial Loan Portfolio [Member]
Summary of nonperforming loans
Total nonperforming TDRs	32,342	29,665	19,779
Total loans	2,298,505	2,264,820	2,100,885
Consumer Loan Portfolio [Member]
Summary of nonperforming loans
Total nonperforming TDRs	17,296	18,901	24,147
Total loans	1,886,756	1,902,915	1,742,213
Nonperforming [Member]
Summary of nonperforming loans
Total nonaccrual loans	66,251	71,298	79,153
Total accruing loans contractually past due 90 days or more as to interest or principal payments	1,251	2,359	2,646
Total nonperforming TDRs	18,915	17,197	16,749
Total loans	86,417	90,854	98,548
Nonperforming [Member] | Commercial Loan Portfolio [Member]
Summary of nonperforming loans
Total nonperforming TDRs	14,587	13,876	11,258
Nonperforming [Member] | Consumer Loan Portfolio [Member]
Summary of nonperforming loans
Total nonperforming TDRs	4,328	3,321	5,491
Nonperforming [Member] | Commercial [Member]
Summary of nonperforming loans
Total nonaccrual loans	12,186	14,601	11,443
Total accruing loans contractually past due 90 days or more as to interest or principal payments	4	0	1,005
Nonperforming [Member] | Real estate commercial [Member]
Summary of nonperforming loans
Total nonaccrual loans	35,849	37,660	46,870
Total accruing loans contractually past due 90 days or more as to interest or principal payments	177	87	75
Nonperforming [Member] | Real Estate Construction Loans [Member]
Summary of nonperforming loans
Total nonaccrual loans	168	1,217	61
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	4,105	4,184	3,748
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	10,407	10,164	12,687
Total accruing loans contractually past due 90 days or more as to interest or principal payments	196	1,503	333
Nonperforming [Member] | Consumer Installment Loans [Member]
Summary of nonperforming loans
Total nonaccrual loans	699	739	1,278
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	2,837	2,733	3,066
Total accruing loans contractually past due 90 days or more as to interest or principal payments	$ 874	$ 769	$ 1,233