Loans (Summary of Nonperforming Loans) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015
Summary of nonperforming loans
Total TDRs	$ 100,764	$ 103,111	$ 101,824
Total loans	$ 7,366,885	7,271,147	5,702,874
Minimum number of days accruing loans past due move to nonaccrual status	90 days
Commercial Loan Portfolio [Member]
Summary of nonperforming loans
Total TDRs	$ 76,615	78,823	77,511
Total loans	4,308,209	4,250,117	3,081,931
Consumer Loan Portfolio [Member]
Summary of nonperforming loans
Total TDRs	24,149	24,288	24,313
Total loans	3,058,676	3,021,030	2,620,943
Nonperforming [Member]
Summary of nonperforming loans
Total nonaccrual loans	53,419	62,225	53,440
Total accruing loans contractually past due 90 days or more as to interest or principal payments	1,472	2,287	801
Total TDRs	18,364	19,368	18,500
Total loans	73,255	83,880	72,741
Nonperforming [Member] | Commercial Loan Portfolio [Member]
Summary of nonperforming loans
Total TDRs	15,351	16,297	15,810
Nonperforming [Member] | Consumer Loan Portfolio [Member]
Summary of nonperforming loans
Total TDRs	3,013	3,071	2,690
Nonperforming [Member] | Commercial [Member]
Summary of nonperforming loans
Total nonaccrual loans	19,264	28,554	18,904
Total accruing loans contractually past due 90 days or more as to interest or principal payments	370	364	52
Nonperforming [Member] | Real estate commercial [Member]
Summary of nonperforming loans
Total nonaccrual loans	25,859	25,163	24,766
Total accruing loans contractually past due 90 days or more as to interest or principal payments	0	254	148
Nonperforming [Member] | Real Estate Construction Loans [Member]
Summary of nonperforming loans
Total nonaccrual loans	546	521	953
Nonperforming [Member] | Real estate residential [Member]
Summary of nonperforming loans
Total nonaccrual loans	5,062	5,557	6,514
Total accruing loans contractually past due 90 days or more as to interest or principal payments	423	402	172
Nonperforming [Member] | Consumer Installment Loans [Member]
Summary of nonperforming loans
Total nonaccrual loans	360	451	433
Nonperforming [Member] | Home Equity Loans [Member]
Summary of nonperforming loans
Total nonaccrual loans	2,328	1,979	1,870
Total accruing loans contractually past due 90 days or more as to interest or principal payments	$ 679	$ 1,267	$ 429