Loans (Summary of Nonperforming Loans) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014
Summary of nonperforming loans
Total TDRs	$ 101,824	$ 101,322	$ 103,671
Total loans	5,702,874	5,688,230	4,753,289
Minimum number of days accruing loans past due move to nonaccrual status	90 days
Commercial Loan Portfolio [Member]
Summary of nonperforming loans
Total TDRs	77,511	77,047	79,852
Total loans	3,081,931	3,084,024	2,586,653
Consumer Loan Portfolio [Member]
Summary of nonperforming loans
Total TDRs	24,313	24,275	23,819
Total loans	2,620,943	2,604,206	2,166,636
Nonperforming [Member]
Summary of nonperforming loans
Total nonaccrual loans	53,440	50,644	57,687
Total accruing loans contractually past due 90 days or more as to interest or principal payments	801	2,073	1,395
Total TDRs	18,500	18,467	17,462
Total loans	72,741	71,184	76,544
Nonperforming [Member] | Commercial Loan Portfolio [Member]
Summary of nonperforming loans
Total TDRs	15,810	15,271	11,218
Nonperforming [Member] | Consumer Loan Portfolio [Member]
Summary of nonperforming loans
Total TDRs	2,690	3,196	6,244
Nonperforming [Member] | Commercial [Member]
Summary of nonperforming loans
Total nonaccrual loans	18,904	16,418	18,251
Total accruing loans contractually past due 90 days or more as to interest or principal payments	52	170	43
Nonperforming [Member] | Real estate commercial [Member]
Summary of nonperforming loans
Total nonaccrual loans	24,766	24,966	27,568
Total accruing loans contractually past due 90 days or more as to interest or principal payments	148	0	730
Nonperforming [Member] | Real Estate Construction Loans [Member]
Summary of nonperforming loans
Total nonaccrual loans	663	162	160
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	290	225	2,267
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	6,514	6,706	6,589
Total accruing loans contractually past due 90 days or more as to interest or principal payments	172	557	0
Nonperforming [Member] | Consumer Installment Loans [Member]
Summary of nonperforming loans
Total nonaccrual loans	433	500	806
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	1,870	1,667	2,046
Total accruing loans contractually past due 90 days or more as to interest or principal payments	$ 429	$ 1,346	$ 622