Loans (Summary of Nonperforming Loans) (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014
Summary of nonperforming loans
Total TDRs	$ 98,988	$ 101,322	$ 100,577
Total loans	$ 7,216,195	5,688,230	5,040,920
Minimum number of days accruing loans past due move to nonaccrual status	90 days
Commercial Loan Portfolio [Member]
Summary of nonperforming loans
Total TDRs	$ 74,398	77,047	76,952
Total loans	4,202,815	3,084,024	2,698,808
Consumer Loan Portfolio [Member]
Summary of nonperforming loans
Total TDRs	24,590	24,275	23,625
Total loans	3,013,380	2,604,206	2,342,112
Nonperforming [Member]
Summary of nonperforming loans
Total nonaccrual loans	60,636	50,644	53,036
Total accruing loans contractually past due 90 days or more as to interest or principal payments	1,468	2,073	2,262
Total TDRs	19,113	18,467	15,444
Total loans	81,217	71,184	70,742
Nonperforming [Member] | Commercial Loan Portfolio [Member]
Summary of nonperforming loans
Total TDRs	15,559	15,271	11,797
Nonperforming [Member] | Consumer Loan Portfolio [Member]
Summary of nonperforming loans
Total TDRs	3,554	3,196	3,647
Nonperforming [Member] | Commercial [Member]
Summary of nonperforming loans
Total nonaccrual loans	26,463	16,418	18,213
Total accruing loans contractually past due 90 days or more as to interest or principal payments	122	170	16
Nonperforming [Member] | Real estate commercial [Member]
Summary of nonperforming loans
Total nonaccrual loans	24,969	24,966	23,858
Total accruing loans contractually past due 90 days or more as to interest or principal payments	216	0	87
Nonperforming [Member] | Real Estate Construction Loans [Member]
Summary of nonperforming loans
Total nonaccrual loans	247	162	162
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	297	225	1,467
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	6,248	6,706	6,693
Total accruing loans contractually past due 90 days or more as to interest or principal payments	572	557	380
Nonperforming [Member] | Consumer Installment Loans [Member]
Summary of nonperforming loans
Total nonaccrual loans	536	500	527
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	1,876	1,667	2,116
Total accruing loans contractually past due 90 days or more as to interest or principal payments	$ 558	$ 1,346	$ 1,779