Allowance for Loan and Lease Losses - Credit Risk Profiles (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($) factor	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Credit quality
Percentage of loans sold with no recourse not subject to grading	100.00%
Number of risk factors in internal loan rating system | factor	8
Loans and leases	$ 13,076,191	$ 12,277,369	$ 11,520,378
Loss
Credit quality
Loans and leases	0	0
Commercial Lending
Credit quality
Loans and leases	6,974,069	6,600,840
Commercial Lending | Pass
Credit quality
Loans and leases	6,718,416	6,445,576
Commercial Lending | Special mention
Credit quality
Loans and leases	149,733	73,876
Commercial Lending | Substandard
Credit quality
Loans and leases	105,728	79,674
Commercial Lending | Doubtful
Credit quality
Loans and leases	192	1,714
Commercial and Industrial
Credit quality
Loans and leases	3,208,760	3,135,266	3,239,600
Commercial and Industrial | Pass
Credit quality
Loans and leases	3,069,546	3,035,121
Commercial and Industrial | Special mention
Credit quality
Loans and leases	57,012	43,435
Commercial and Industrial | Substandard
Credit quality
Loans and leases	82,010	54,996
Commercial and Industrial | Doubtful
Credit quality
Loans and leases	192	1,714
Commercial Real Estate
Credit quality
Loans and leases	2,990,783	2,667,597	2,343,495
Commercial Real Estate | Pass
Credit quality
Loans and leases	2,876,907	2,619,494
Commercial Real Estate | Special mention
Credit quality
Loans and leases	91,298	26,248
Commercial Real Estate | Substandard
Credit quality
Loans and leases	22,578	21,855
Construction
Credit quality
Loans and leases	626,757	632,911	450,012
Construction | Pass
Credit quality
Loans and leases	625,607	628,112
Construction | Special mention
Credit quality
Loans and leases	200	2,377
Construction | Substandard
Credit quality
Loans and leases	950	2,422
Lease Financing
Credit quality
Loans and leases	147,769	165,066	180,040
Lease Financing | Pass
Credit quality
Loans and leases	146,356	162,849
Lease Financing | Special mention
Credit quality
Loans and leases	1,223	1,816
Lease Financing | Substandard
Credit quality
Loans and leases	190	401
Residential and consumer
Credit quality
Loans and leases	6,102,122	5,676,529
Residential and consumer | Performing
Credit quality
Loans and leases	6,040,469	5,630,723
Residential and consumer | Non-performing and delinquent
Credit quality
Loans and leases	61,653	45,806
Residential
Credit quality
Loans and leases, Residential Mortgage	3,527,101	3,226,601
Loans and leases	4,439,618	4,090,053	3,796,459
Residential | Performing
Credit quality
Loans and leases, Residential Mortgage	3,519,172	3,215,329
Residential | Non-performing and delinquent
Credit quality
Loans and leases, Residential Mortgage	7,929	11,272
Home Equity Line
Credit quality
Loans and leases	912,517	863,452
Home Equity Line | Performing
Credit quality
Loans and leases	903,284	858,505
Home Equity Line | Non-performing and delinquent
Credit quality
Loans and leases	9,233	4,947
Consumer
Credit quality
Loans and leases	1,662,504	1,586,476	$ 1,510,772
Consumer loans | Consumer
Credit quality
Loans and leases	239,906	234,358
Consumer loans | Consumer | Performing
Credit quality
Loans and leases	234,458	231,023
Consumer loans | Consumer | Non-performing and delinquent
Credit quality
Loans and leases	5,448	3,335
Consumer - Auto | Consumer
Credit quality
Loans and leases	1,078,132	1,023,697
Consumer - Auto | Consumer | Performing
Credit quality
Loans and leases	1,044,393	1,001,085
Consumer - Auto | Consumer | Non-performing and delinquent
Credit quality
Loans and leases	33,739	22,612
Credit Cards | Consumer
Credit quality
Loans and leases	344,466	328,421
Credit Cards | Consumer | Performing
Credit quality
Loans and leases	339,162	324,781
Credit Cards | Consumer | Non-performing and delinquent
Credit quality
Loans and leases	$ 5,304	$ 3,640