Loans (Summary of Nonperforming Loans) (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2013
Summary of nonperforming loans
Total TDRs	$ 100,577	$ 94,943	$ 92,017
Total loans	5,040,920	4,647,621	4,522,671
Minimum number of days accruing loans past due move to nonaccrual status	90 days
Commercial Loan Portfolio [Member]
Summary of nonperforming loans
Total TDRs	76,952	72,214	69,337
Total loans	2,698,808	2,518,826	2,445,787
Consumer Loan Portfolio [Member]
Summary of nonperforming loans
Total TDRs	23,625	22,729	22,680
Total loans	2,342,112	2,128,795	2,076,884
Nonperforming [Member]
Summary of nonperforming loans
Total nonaccrual loans	53,036	61,897	55,286
Total accruing loans contractually past due 90 days or more as to interest or principal payments	2,262	1,997	1,659
Total TDRs	15,444	18,090	18,873
Total loans	70,742	81,984	75,818
Nonperforming [Member] | Commercial Loan Portfolio [Member]
Summary of nonperforming loans
Total TDRs	11,797	13,414	15,744
Nonperforming [Member] | Consumer Loan Portfolio [Member]
Summary of nonperforming loans
Total TDRs	3,647	4,676	3,129
Nonperforming [Member] | Commercial [Member]
Summary of nonperforming loans
Total nonaccrual loans	18,213	18,374	11,809
Total accruing loans contractually past due 90 days or more as to interest or principal payments	16	536	281
Nonperforming [Member] | Real estate commercial [Member]
Summary of nonperforming loans
Total nonaccrual loans	23,858	28,598	28,623
Total accruing loans contractually past due 90 days or more as to interest or principal payments	87	190	0
Nonperforming [Member] | Real Estate Construction Loans [Member]
Summary of nonperforming loans
Total nonaccrual loans	162	371	183
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	1,467	2,309	2,954
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	6,693	8,921	8,029
Total accruing loans contractually past due 90 days or more as to interest or principal payments	380	537	692
Nonperforming [Member] | Consumer Installment Loans [Member]
Summary of nonperforming loans
Total nonaccrual loans	527	676	665
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	2,116	2,648	3,023
Total accruing loans contractually past due 90 days or more as to interest or principal payments	$ 1,779	$ 734	$ 686