Allowance for Loan and Lease Losses - Credit Risk Profiles (Details) $ in Thousands	6 Months Ended
	Jun. 30, 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	$ 12,637,686	$ 12,277,369
Loss
Credit quality
Loans and leases	0	0
Commercial Lending
Credit quality
Loans and leases	6,769,515	6,600,840
Commercial Lending | Pass
Credit quality
Loans and leases	6,499,646	6,445,576
Commercial Lending | Special mention
Credit quality
Loans and leases	169,401	73,876
Commercial Lending | Substandard
Credit quality
Loans and leases	98,909	79,674
Commercial Lending | Doubtful
Credit quality
Loans and leases	1,559	1,714
Commercial and Industrial
Credit quality
Loans and leases	3,116,145	3,135,266
Commercial and Industrial | Pass
Credit quality
Loans and leases	2,971,359	3,035,121
Commercial and Industrial | Special mention
Credit quality
Loans and leases	72,534	43,435
Commercial and Industrial | Substandard
Credit quality
Loans and leases	70,693	54,996
Commercial and Industrial | Doubtful
Credit quality
Loans and leases	1,559	1,714
Commercial Real Estate
Credit quality
Loans and leases	2,837,520	2,667,597
Commercial Real Estate | Pass
Credit quality
Loans and leases	2,736,004	2,619,494
Commercial Real Estate | Special mention
Credit quality
Loans and leases	76,822	26,248
Commercial Real Estate | Substandard
Credit quality
Loans and leases	24,694	21,855
Construction
Credit quality
Loans and leases	654,084	632,911
Construction | Pass
Credit quality
Loans and leases	632,379	628,112
Construction | Special mention
Credit quality
Loans and leases	18,494	2,377
Construction | Substandard
Credit quality
Loans and leases	3,211	2,422
Lease Financing
Credit quality
Loans and leases	161,766	165,066
Lease Financing | Pass
Credit quality
Loans and leases	159,904	162,849
Lease Financing | Special mention
Credit quality
Loans and leases	1,551	1,816
Lease Financing | Substandard
Credit quality
Loans and leases	311	401
Residential and consumer
Credit quality
Loans and leases	5,868,171	5,676,529
Residential and consumer | Performing
Credit quality
Loans and leases	5,827,171	5,630,723
Residential and consumer | Non-performing and delinquent
Credit quality
Loans and leases	41,000	45,806
Residential
Credit quality
Loans and leases	4,236,083	4,090,053
Residential | Performing
Credit quality
Loans and leases	4,221,570	4,073,834
Residential | Non-performing and delinquent
Credit quality
Loans and leases	14,513	16,219
Consumer
Credit quality
Loans and leases	1,632,088	1,586,476
Consumer loans | Consumer
Credit quality
Loans and leases	232,819	234,358
Consumer loans | Consumer | Performing
Credit quality
Loans and leases	230,141	231,023
Consumer loans | Consumer | Non-performing and delinquent
Credit quality
Loans and leases	2,678	3,335
Consumer - Auto | Consumer
Credit quality
Loans and leases	1,073,808	1,023,697
Consumer - Auto | Consumer | Performing
Credit quality
Loans and leases	1,053,187	1,001,085
Consumer - Auto | Consumer | Non-performing and delinquent
Credit quality
Loans and leases	20,621	22,612
Credit Cards | Consumer
Credit quality
Loans and leases	325,461	328,421
Credit Cards | Consumer | Performing
Credit quality
Loans and leases	322,273	324,781
Credit Cards | Consumer | Non-performing and delinquent
Credit quality
Loans and leases	$ 3,188	$ 3,640