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		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018
Allowance for Loan and Lease Losses:
Balance at Beginning of Period	$ 107,672	$ 108,188	$ 106,693	$ 107,346
Loans and Leases Charged-Off	(5,755)	(6,027)	(17,712)	(17,676)
Recoveries on Loans and Leases Previously Charged-Off	2,769	2,729	8,705	7,595
Net Loans and Leases Recovered (Charged-Off)	(2,986)	(3,298)	(9,007)	(10,081)
Provision for Credit Losses	4,250	3,800	11,250	11,425
Balance at End of Period	108,936	108,690	108,936	108,690
Allowance for Loan and Lease Losses:
Individually Evaluated for Impairment					$ 3,381		$ 3,945
Collectively Evaluated for Impairment					105,555		104,745
Total	107,672	108,188	108,936	107,346	108,936	$ 106,693	108,690
Recorded Investment in Loans and Leases:
Individually Evaluated for Impairment					59,989		54,408
Collectively Evaluated for Impairment					10,821,309		10,176,654
Total Loans and Leases					10,881,298	10,448,774	10,231,062
Commercial
Allowance for Loan and Lease Losses:
Balance at Beginning of Period	69,268	63,712	66,874	65,822
Loans and Leases Charged-Off	(239)	(449)	(2,431)	(1,140)
Recoveries on Loans and Leases Previously Charged-Off	318	542	1,220	1,236
Net Loans and Leases Recovered (Charged-Off)	79	93	(1,211)	96
Provision for Credit Losses	1,023	1,274	4,707	(839)
Balance at End of Period	70,370	65,079	70,370	65,079
Allowance for Loan and Lease Losses:
Individually Evaluated for Impairment					115		135
Collectively Evaluated for Impairment					70,255		64,944
Total	69,268	63,712	70,370	65,822	70,370	66,874	65,079
Recorded Investment in Loans and Leases:
Individually Evaluated for Impairment					19,324		12,190
Collectively Evaluated for Impairment					4,137,409		3,888,118
Total Loans and Leases					4,156,733	3,979,792	3,900,308
Consumer
Allowance for Loan and Lease Losses:
Balance at Beginning of Period	38,404	44,476	39,819	41,524
Loans and Leases Charged-Off	(5,516)	(5,578)	(15,281)	(16,536)
Recoveries on Loans and Leases Previously Charged-Off	2,451	2,187	7,485	6,359
Net Loans and Leases Recovered (Charged-Off)	(3,065)	(3,391)	(7,796)	(10,177)
Provision for Credit Losses	3,227	2,526	6,543	12,264
Balance at End of Period	38,566	43,611	38,566	43,611
Allowance for Loan and Lease Losses:
Individually Evaluated for Impairment					3,266		3,810
Collectively Evaluated for Impairment					35,300		39,801
Total	$ 38,404	$ 44,476	$ 39,819	$ 43,611	38,566	39,819	43,611
Recorded Investment in Loans and Leases:
Individually Evaluated for Impairment					40,665		42,218
Collectively Evaluated for Impairment					6,683,900		6,288,536
Total Loans and Leases					$ 6,724,565	$ 6,468,982	$ 6,330,754