Loans and Leases and the Allowance for Loan and Lease Losses (Allowance for Loan and Lease Losses) (Details 2) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Allowance for Loan and Lease Losses:
Balance at the Beginning of Period	$ 104,273	$ 102,880	$ 108,688
Loans and Leases Charged-Off	(23,255)	(18,509)	(16,439)
Recoveries on Loans and Leases Previously Charged-Off	9,428	15,152	9,631
Net Loans and Leases Recovered (Charged-Off)	(13,827)	(3,357)	(6,808)
Provision for Credit Losses	16,900	4,750	1,000
Balance at End of Period	107,346	104,273	102,880
Allowance for Loan and Lease Losses:
Individually Evaluated for Impairment				$ 3,916	$ 3,555	$ 3,578
Collectively Evaluated for Impairment				103,430	100,718	99,302
Total	104,273	102,880	108,688	107,346	104,273	102,880
Recorded Investment in Loans and Leases:
Individually Evaluated for Impairment				61,218	60,698	66,697
Collectively Evaluated for Impairment				9,735,729	8,889,087	7,812,288
Total Loans and Leases				9,796,947	8,949,785	7,878,985
Commercial
Allowance for Loan and Lease Losses:
Balance at the Beginning of Period	65,680	60,714	64,551
Loans and Leases Charged-Off	(1,408)	(865)	(954)
Recoveries on Loans and Leases Previously Charged-Off	1,485	8,137	2,173
Net Loans and Leases Recovered (Charged-Off)	77	7,272	1,219
Provision for Credit Losses	65	(2,306)	(5,056)
Balance at End of Period	65,822	65,680	60,714
Allowance for Loan and Lease Losses:
Individually Evaluated for Impairment				141	45	205
Collectively Evaluated for Impairment				65,681	65,635	60,509
Total	65,680	60,714	64,551	65,822	65,680	60,714
Recorded Investment in Loans and Leases:
Individually Evaluated for Impairment				20,216	21,572	27,950
Collectively Evaluated for Impairment				3,746,282	3,596,120	3,125,902
Total Loans and Leases				3,766,498	3,617,692	3,153,852
Consumer
Allowance for Loan and Lease Losses:
Balance at the Beginning of Period	38,593	42,166	44,137
Loans and Leases Charged-Off	(21,847)	(17,644)	(15,485)
Recoveries on Loans and Leases Previously Charged-Off	7,943	7,015	7,458
Net Loans and Leases Recovered (Charged-Off)	(13,904)	(10,629)	(8,027)
Provision for Credit Losses	16,835	7,056	6,056
Balance at End of Period	41,524	38,593	42,166
Allowance for Loan and Lease Losses:
Individually Evaluated for Impairment				3,775	3,510	3,373
Collectively Evaluated for Impairment				37,749	35,083	38,793
Total	$ 38,593	$ 42,166	$ 44,137	41,524	38,593	42,166
Recorded Investment in Loans and Leases:
Individually Evaluated for Impairment				41,002	39,126	38,747
Collectively Evaluated for Impairment				5,989,447	5,292,967	4,686,386
Total Loans and Leases				$ 6,030,449	$ 5,332,093	$ 4,725,133