Loans and Leases and the Allowance for Loan and Lease Losses (Aging Analysis) (Details 4) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Non-Accrual	$ 15,080	$ 18,075
Total Past Due and Non-Accrual	61,352	67,494
Current	9,735,595	8,882,291
Total Loans and Leases	9,796,947	8,949,785	$ 7,878,985
Non-Accrual Loans and Leases that are Current	$ 2,896	3,059
Number of days non-accrual loans and leases are not past due	30 days
30 to 59 Days Past Due
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	$ 29,465	35,272
60 to 89 Days Past Due
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	9,660	7,077
Past Due 90 Days or More
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	7,147	7,070
Commercial
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Non-Accrual	1,846	1,148
Total Past Due and Non-Accrual	7,274	13,007
Current	3,759,224	3,604,685
Total Loans and Leases	3,766,498	3,617,692	3,153,852
Non-Accrual Loans and Leases that are Current	778	416
Commercial | 30 to 59 Days Past Due
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	4,383	10,826
Commercial | 60 to 89 Days Past Due
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	1,045	1,033
Commercial | Past Due 90 Days or More
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	0	0
Commercial | Commercial and Industrial
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Non-Accrual	448	151
Total Past Due and Non-Accrual	5,285	11,865
Current	1,274,062	1,237,926
Total Loans and Leases	1,279,347	1,249,791
Non-Accrual Loans and Leases that are Current	313	0
Commercial | Commercial and Industrial | 30 to 59 Days Past Due
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	4,196	10,698
Commercial | Commercial and Industrial | 60 to 89 Days Past Due
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	641	1,016
Commercial | Commercial and Industrial | Past Due 90 Days or More
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	0	0
Commercial | Commercial Mortgage
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Non-Accrual	1,398	997
Total Past Due and Non-Accrual	1,989	1,142
Current	2,101,978	1,888,409
Total Loans and Leases	2,103,967	1,889,551
Non-Accrual Loans and Leases that are Current	465	416
Commercial | Commercial Mortgage | 30 to 59 Days Past Due
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	187	128
Commercial | Commercial Mortgage | 60 to 89 Days Past Due
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	404	17
Commercial | Commercial Mortgage | Past Due 90 Days or More
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	0	0
Commercial | Construction
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Non-Accrual	0	0
Total Past Due and Non-Accrual	0	0
Current	202,253	270,018
Total Loans and Leases	202,253	270,018
Non-Accrual Loans and Leases that are Current	0	0
Commercial | Construction | 30 to 59 Days Past Due
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	0	0
Commercial | Construction | 60 to 89 Days Past Due
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	0	0
Commercial | Construction | Past Due 90 Days or More
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	0	0
Commercial | Lease Financing
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Non-Accrual	0	0
Total Past Due and Non-Accrual	0	0
Current	180,931	208,332
Total Loans and Leases	180,931	208,332
Non-Accrual Loans and Leases that are Current	0	0
Commercial | Lease Financing | 30 to 59 Days Past Due
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	0	0
Commercial | Lease Financing | 60 to 89 Days Past Due
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	0	0
Commercial | Lease Financing | Past Due 90 Days or More
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	0	0
Consumer
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Non-Accrual	13,234	16,927
Total Past Due and Non-Accrual	54,078	54,487
Current	5,976,371	5,277,606
Total Loans and Leases	6,030,449	5,332,093	$ 4,725,133
Non-Accrual Loans and Leases that are Current	2,118	2,643
Consumer | 30 to 59 Days Past Due
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	25,082	24,446
Consumer | 60 to 89 Days Past Due
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	8,615	6,044
Consumer | Past Due 90 Days or More
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	7,147	7,070
Consumer | Residential Mortgage
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Non-Accrual	9,243	13,780
Total Past Due and Non-Accrual	21,769	23,504
Current	3,445,004	3,139,569
Total Loans and Leases	3,466,773	3,163,073
Non-Accrual Loans and Leases that are Current	806	1,628
Consumer | Residential Mortgage | 30 to 59 Days Past Due
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	7,815	6,491
Consumer | Residential Mortgage | 60 to 89 Days Past Due
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	2,008	106
Consumer | Residential Mortgage | Past Due 90 Days or More
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	2,703	3,127
Consumer | Home Equity
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Non-Accrual	3,991	3,147
Total Past Due and Non-Accrual	10,883	9,911
Current	1,574,572	1,324,252
Total Loans and Leases	1,585,455	1,334,163
Non-Accrual Loans and Leases that are Current	1,312	1,015
Consumer | Home Equity | 30 to 59 Days Past Due
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	2,532	3,063
Consumer | Home Equity | 60 to 89 Days Past Due
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	2,736	2,244
Consumer | Home Equity | Past Due 90 Days or More
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	1,624	1,457
Consumer | Automobile
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Non-Accrual	0	0
Total Past Due and Non-Accrual	14,846	14,748
Current	513,628	439,585
Total Loans and Leases	528,474	454,333
Non-Accrual Loans and Leases that are Current	0	0
Consumer | Automobile | 30 to 59 Days Past Due
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	11,728	11,692
Consumer | Automobile | 60 to 89 Days Past Due
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	2,232	2,162
Consumer | Automobile | Past Due 90 Days or More
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	886	894
Consumer | Other
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Non-Accrual	0	0
Total Past Due and Non-Accrual	6,580	6,324
Current	443,167	374,200
Total Loans and Leases	449,747	380,524
Non-Accrual Loans and Leases that are Current	0	0
Consumer | Other | 30 to 59 Days Past Due
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	3,007	3,200
Consumer | Other | 60 to 89 Days Past Due
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	1,639	1,532
Consumer | Other | Past Due 90 Days or More
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	$ 1,934	$ 1,592