Allowance for Loan and Lease Losses - Credit Risk Profiles (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2018 USD ($) factor	Dec. 31, 2017 USD ($)
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	$ 12,464,165	$ 12,277,369
Loss
Credit quality
Loans and leases	0	0
Commercial Lending
Credit quality
Loans and leases	6,712,173	6,600,840
Commercial Lending | Pass
Credit quality
Loans and leases	6,453,397	6,445,576
Commercial Lending | Special mention
Credit quality
Loans and leases	180,740	73,876
Commercial Lending | Substandard
Credit quality
Loans and leases	76,475	79,674
Commercial Lending | Doubtful
Credit quality
Loans and leases	1,561	1,714
Commercial and Industrial
Credit quality
Loans and leases	3,219,210	3,135,266
Commercial and Industrial | Pass
Credit quality
Loans and leases	3,065,462	3,035,121
Commercial and Industrial | Special mention
Credit quality
Loans and leases	100,677	43,435
Commercial and Industrial | Substandard
Credit quality
Loans and leases	51,510	54,996
Commercial and Industrial | Doubtful
Credit quality
Loans and leases	1,561	1,714
Commercial Real Estate
Credit quality
Loans and leases	2,738,557	2,667,597
Commercial Real Estate | Pass
Credit quality
Loans and leases	2,640,740	2,619,494
Commercial Real Estate | Special mention
Credit quality
Loans and leases	75,962	26,248
Commercial Real Estate | Substandard
Credit quality
Loans and leases	21,855	21,855
Construction
Credit quality
Loans and leases	594,266	632,911
Construction | Pass
Credit quality
Loans and leases	589,090	628,112
Construction | Special mention
Credit quality
Loans and leases	2,417	2,377
Construction | Substandard
Credit quality
Loans and leases	2,759	2,422
Lease Financing
Credit quality
Loans and leases	160,140	165,066
Lease Financing | Pass
Credit quality
Loans and leases	158,105	162,849
Lease Financing | Special mention
Credit quality
Loans and leases	1,684	1,816
Lease Financing | Substandard
Credit quality
Loans and leases	351	401
Residential and consumer
Credit quality
Loans and leases	5,751,992	5,676,529
Residential and consumer | Performing
Credit quality
Loans and leases	5,713,341	5,630,723
Residential and consumer | Non-performing and delinquent
Credit quality
Loans and leases	38,651	45,806
Residential
Credit quality
Loans and leases	4,156,003	4,090,053
Residential | Performing
Credit quality
Loans and leases	4,142,201	4,073,834
Residential | Non-performing and delinquent
Credit quality
Loans and leases	13,802	16,219
Consumer
Credit quality
Loans and leases	1,595,989	1,586,476
Consumer loans | Consumer
Credit quality
Loans and leases	225,333	234,358
Consumer loans | Consumer | Performing
Credit quality
Loans and leases	222,434	231,023
Consumer loans | Consumer | Non-performing and delinquent
Credit quality
Loans and leases	2,899	3,335
Consumer - Auto | Consumer
Credit quality
Loans and leases	1,051,778	1,023,697
Consumer - Auto | Consumer | Performing
Credit quality
Loans and leases	1,033,161	1,001,085
Consumer - Auto | Consumer | Non-performing and delinquent
Credit quality
Loans and leases	18,617	22,612
Credit Cards | Consumer
Credit quality
Loans and leases	318,878	328,421
Credit Cards | Consumer | Performing
Credit quality
Loans and leases	315,545	324,781
Credit Cards | Consumer | Non-performing and delinquent
Credit quality
Loans and leases	$ 3,333	$ 3,640