Loans (Summary of Nonperforming Loans) (Details) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2012
Summary of nonperforming loans
Total nonperforming TDRs	$ 55,043	$ 48,566	$ 42,172
Total loans	4,335,871	4,167,735	3,962,342
Number of minimum days for performing and nonperforming trouble debt restructuring	90 days
Commercial Loan Portfolio [Member]
Summary of nonperforming loans
Total nonperforming TDRs	37,637	29,665	23,773
Total loans	2,364,870	2,264,820	2,129,234
Consumer Loan Portfolio [Member]
Summary of nonperforming loans
Total nonperforming TDRs	17,406	18,901	18,399
Total loans	1,971,001	1,902,915	1,833,108
Nonperforming [Member]
Summary of nonperforming loans
Total nonaccrual loans	56,024	71,298	74,456
Total accruing loans contractually past due 90 days or more as to interest or principal payments	932	2,359	2,566
Total nonperforming TDRs	22,386	17,197	15,789
Total loans	79,342	90,854	92,811
Nonperforming [Member] | Commercial Loan Portfolio [Member]
Summary of nonperforming loans
Total nonperforming TDRs	19,140	13,876	11,691
Nonperforming [Member] | Consumer Loan Portfolio [Member]
Summary of nonperforming loans
Total nonperforming TDRs	3,246	3,321	4,098
Nonperforming [Member] | Commercial [Member]
Summary of nonperforming loans
Total nonaccrual loans	11,052	14,601	12,673
Total accruing loans contractually past due 90 days or more as to interest or principal payments	1	0	300
Nonperforming [Member] | Real estate commercial [Member]
Summary of nonperforming loans
Total nonaccrual loans	28,498	37,660	41,691
Total accruing loans contractually past due 90 days or more as to interest or principal payments	78	87	269
Nonperforming [Member] | Real Estate Construction Loans [Member]
Summary of nonperforming loans
Total nonaccrual loans	183	1,217	408
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	3,434	4,184	3,077
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	9,241	10,164	12,613
Total accruing loans contractually past due 90 days or more as to interest or principal payments	164	1,503	840
Nonperforming [Member] | Consumer Installment Loans [Member]
Summary of nonperforming loans
Total nonaccrual loans	552	739	1,182
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	3,064	2,733	2,812
Total accruing loans contractually past due 90 days or more as to interest or principal payments	$ 689	$ 769	$ 1,157