Allowance for Loan and Lease Losses - Credit Risk Profiles (Details) $ in Thousands	9 Months Ended
	Sep. 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	$ 12,600,464	$ 12,277,369
Loss
Credit quality
Loans and leases	0	0
Commercial Lending
Credit quality
Loans and leases	6,635,098	6,600,840
Commercial Lending | Pass
Credit quality
Loans and leases	6,396,399	6,445,576
Commercial Lending | Special mention
Credit quality
Loans and leases	138,132	73,876
Commercial Lending | Substandard
Credit quality
Loans and leases	100,375	79,674
Commercial Lending | Doubtful
Credit quality
Loans and leases	192	1,714
Commercial and Industrial
Credit quality
Loans and leases	2,969,237	3,135,266
Commercial and Industrial | Pass
Credit quality
Loans and leases	2,831,415	3,035,121
Commercial and Industrial | Special mention
Credit quality
Loans and leases	64,966	43,435
Commercial and Industrial | Substandard
Credit quality
Loans and leases	72,664	54,996
Commercial and Industrial | Doubtful
Credit quality
Loans and leases	192	1,714
Commercial Real Estate
Credit quality
Loans and leases	2,891,753	2,667,597
Commercial Real Estate | Pass
Credit quality
Loans and leases	2,797,282	2,619,494
Commercial Real Estate | Special mention
Credit quality
Loans and leases	69,992	26,248
Commercial Real Estate | Substandard
Credit quality
Loans and leases	24,479	21,855
Construction
Credit quality
Loans and leases	612,794	632,911
Construction | Pass
Credit quality
Loans and leases	608,201	628,112
Construction | Special mention
Credit quality
Loans and leases	1,630	2,377
Construction | Substandard
Credit quality
Loans and leases	2,963	2,422
Lease Financing
Credit quality
Loans and leases	161,314	165,066
Lease Financing | Pass
Credit quality
Loans and leases	159,501	162,849
Lease Financing | Special mention
Credit quality
Loans and leases	1,544	1,816
Lease Financing | Substandard
Credit quality
Loans and leases	269	401
Residential and consumer
Credit quality
Loans and leases	5,965,366	5,676,529
Residential and consumer | Performing
Credit quality
Loans and leases	5,907,526	5,630,723
Residential and consumer | Non-performing and delinquent
Credit quality
Loans and leases	57,840	45,806
Residential
Credit quality
Loans and leases	4,313,489	4,090,053
Residential | Performing
Credit quality
Loans and leases	4,297,918	4,073,834
Residential | Non-performing and delinquent
Credit quality
Loans and leases	15,571	16,219
Consumer
Credit quality
Loans and leases	1,651,877	1,586,476
Consumer loans | Consumer
Credit quality
Loans and leases	240,577	234,358
Consumer loans | Consumer | Performing
Credit quality
Loans and leases	235,072	231,023
Consumer loans | Consumer | Non-performing and delinquent
Credit quality
Loans and leases	5,505	3,335
Consumer - Auto | Consumer
Credit quality
Loans and leases	1,082,301	1,023,697
Consumer - Auto | Consumer | Performing
Credit quality
Loans and leases	1,049,219	1,001,085
Consumer - Auto | Consumer | Non-performing and delinquent
Credit quality
Loans and leases	33,082	22,612
Credit Cards | Consumer
Credit quality
Loans and leases	328,999	328,421
Credit Cards | Consumer | Performing
Credit quality
Loans and leases	325,317	324,781
Credit Cards | Consumer | Non-performing and delinquent
Credit quality
Loans and leases	$ 3,682	$ 3,640