Loans and Leases and the Allowance for Loan and Lease Losses (Allowance for Loan and Lease Losses) (Details 2) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017
Allowance for Loan and Lease Losses:
Balance at Beginning of Period	$ 107,346	$ 104,273
Loans and Leases Charged-Off	(5,988)	(5,704)
Recoveries on Loans and Leases Previously Charged-Off	2,455	2,095
Net Loans and Leases Recovered (Charged-Off)	(3,533)	(3,609)
Provision for Credit Losses	4,125	4,400
Balance at End of Period	107,938	105,064
Allowance for Loan and Lease Losses:
Individually Evaluated for Impairment			$ 3,842		$ 3,950
Collectively Evaluated for Impairment			104,096		101,114
Total	107,346	104,273	107,938	$ 107,346	105,064
Recorded Investment in Loans and Leases:
Individually Evaluated for Impairment			61,822		60,331
Collectively Evaluated for Impairment			9,854,806		9,053,478
Total Loans and Leases			9,916,628	9,796,947	9,113,809
Commercial
Allowance for Loan and Lease Losses:
Balance at Beginning of Period	65,822	65,680
Loans and Leases Charged-Off	(206)	(174)
Recoveries on Loans and Leases Previously Charged-Off	328	336
Net Loans and Leases Recovered (Charged-Off)	122	162
Provision for Credit Losses	(1,834)	1,051
Balance at End of Period	64,110	66,893
Allowance for Loan and Lease Losses:
Individually Evaluated for Impairment			59		38
Collectively Evaluated for Impairment			64,051		66,855
Total	65,822	65,680	64,110	65,822	66,893
Recorded Investment in Loans and Leases:
Individually Evaluated for Impairment			21,095		20,902
Collectively Evaluated for Impairment			3,771,641		3,609,593
Total Loans and Leases			3,792,736	3,766,498	3,630,495
Consumer
Allowance for Loan and Lease Losses:
Balance at Beginning of Period	41,524	38,593
Loans and Leases Charged-Off	(5,782)	(5,530)
Recoveries on Loans and Leases Previously Charged-Off	2,127	1,759
Net Loans and Leases Recovered (Charged-Off)	(3,655)	(3,771)
Provision for Credit Losses	5,959	3,349
Balance at End of Period	43,828	38,171
Allowance for Loan and Lease Losses:
Individually Evaluated for Impairment			3,783		3,912
Collectively Evaluated for Impairment			40,045		34,259
Total	$ 41,524	$ 38,593	43,828	41,524	38,171
Recorded Investment in Loans and Leases:
Individually Evaluated for Impairment			40,727		39,429
Collectively Evaluated for Impairment			6,083,165		5,443,885
Total Loans and Leases			$ 6,123,892	$ 6,030,449	$ 5,483,314