Loans and Leases and the Allowance for Loan and Lease Losses (Aging Analysis) (Details 4) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Non-Accrual	$ 15,642	$ 18,075
Total Past Due and Non-Accrual	51,464	67,494
Current	9,522,492	8,882,291
Total Loans and Leases	9,573,956	8,949,785	$ 8,694,097
Non-Accrual Loans and Leases that are Current	$ 3,383	3,059
Number of days non-accrual loans are not past due	30 days
30 - 59 Days Past Due
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	$ 22,325	35,272
60 - 89 Days Past Due
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	6,833	7,077
Past Due 90 Days or More
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	6,664	7,070
Commercial
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Non-Accrual	2,326	1,148
Total Past Due and Non-Accrual	6,540	13,007
Current	3,733,423	3,604,685
Total Loans and Leases	3,739,963	3,617,692	3,489,554
Non-Accrual Loans and Leases that are Current	566	416
Commercial | 30 - 59 Days Past Due
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	3,384	10,826
Commercial | 60 - 89 Days Past Due
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	825	1,033
Commercial | Past Due 90 Days or More
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	5	0
Commercial | Commercial and Industrial
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Non-Accrual	901	151
Total Past Due and Non-Accrual	3,175	11,865
Current	1,249,063	1,237,926
Total Loans and Leases	1,252,238	1,249,791
Non-Accrual Loans and Leases that are Current	162	0
Commercial | Commercial and Industrial | 30 - 59 Days Past Due
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	2,063	10,698
Commercial | Commercial and Industrial | 60 - 89 Days Past Due
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	206	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	5	0
Commercial | Commercial Mortgage
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Non-Accrual	1,425	997
Total Past Due and Non-Accrual	3,365	1,142
Current	2,047,633	1,888,409
Total Loans and Leases	2,050,998	1,889,551
Non-Accrual Loans and Leases that are Current	404	416
Commercial | Commercial Mortgage | 30 - 59 Days Past Due
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	1,321	128
Commercial | Commercial Mortgage | 60 - 89 Days Past Due
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	619	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	232,487	270,018
Total Loans and Leases	232,487	270,018
Non-Accrual Loans and Leases that are Current	0	0
Commercial | Construction | 30 - 59 Days Past Due
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	0	0
Commercial | Construction | 60 - 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	204,240	208,332
Total Loans and Leases	204,240	208,332
Non-Accrual Loans and Leases that are Current	0	0
Commercial | Lease Financing | 30 - 59 Days Past Due
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	0	0
Commercial | Lease Financing | 60 - 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	13,316	16,927
Total Past Due and Non-Accrual	44,924	54,487
Current	5,789,069	5,277,606
Total Loans and Leases	5,833,993	5,332,093	$ 5,204,543
Non-Accrual Loans and Leases that are Current	2,817	2,643
Consumer | 30 - 59 Days Past Due
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	18,941	24,446
Consumer | 60 - 89 Days Past Due
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	6,008	6,044
Consumer | Past Due 90 Days or More
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	6,659	7,070
Consumer | Residential Mortgage
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Non-Accrual	9,188	13,780
Total Past Due and Non-Accrual	17,415	23,504
Current	3,349,219	3,139,569
Total Loans and Leases	3,366,634	3,163,073
Non-Accrual Loans and Leases that are Current	1,517	1,628
Consumer | Residential Mortgage | 30 - 59 Days Past Due
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	3,838	6,491
Consumer | Residential Mortgage | 60 - 89 Days Past Due
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	1,456	106
Consumer | Residential Mortgage | Past Due 90 Days or More
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	2,933	3,127
Consumer | Home Equity
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Non-Accrual	4,128	3,147
Total Past Due and Non-Accrual	9,125	9,911
Current	1,519,228	1,324,252
Total Loans and Leases	1,528,353	1,334,163
Non-Accrual Loans and Leases that are Current	1,300	1,015
Consumer | Home Equity | 30 - 59 Days Past Due
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	2,588	3,063
Consumer | Home Equity | 60 - 89 Days Past Due
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	1,017	2,244
Consumer | Home Equity | Past Due 90 Days or More
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	1,392	1,457
Consumer | Automobile
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Non-Accrual	0	0
Total Past Due and Non-Accrual	12,172	14,748
Current	493,930	439,585
Total Loans and Leases	506,102	454,333
Non-Accrual Loans and Leases that are Current	0	0
Consumer | Automobile | 30 - 59 Days Past Due
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	9,743	11,692
Consumer | Automobile | 60 - 89 Days Past Due
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	1,623	2,162
Consumer | Automobile | Past Due 90 Days or More
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	806	894
Consumer | Other
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Non-Accrual	0	0
Total Past Due and Non-Accrual	6,212	6,324
Current	426,692	374,200
Total Loans and Leases	432,904	380,524
Non-Accrual Loans and Leases that are Current	0	0
Consumer | Other | 30 - 59 Days Past Due
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	2,772	3,200
Consumer | Other | 60 - 89 Days Past Due
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	1,912	1,532
Consumer | Other | Past Due 90 Days or More
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	$ 1,528	$ 1,592