Allowance for Loan and Lease Losses - Credit Risk Profiles (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2017 USD ($) factor	Dec. 31, 2016 USD ($)
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	$ 12,149,711	$ 11,520,378
Loss
Credit quality
Loans and leases	0	0
Commercial Lending
Credit quality
Loans and leases	6,586,061	6,213,147
Commercial Lending | Pass
Credit quality
Loans and leases	6,427,833	6,089,637
Commercial Lending | Special mention
Credit quality
Loans and leases	75,978	69,735
Commercial Lending | Substandard
Credit quality
Loans and leases	80,883	51,856
Commercial Lending | Doubtful
Credit quality
Loans and leases	1,367	1,919
Commercial and Industrial
Credit quality
Loans and leases	3,190,237	3,239,600
Commercial and Industrial | Pass
Credit quality
Loans and leases	3,083,654	3,166,304
Commercial and Industrial | Special mention
Credit quality
Loans and leases	46,093	41,719
Commercial and Industrial | Substandard
Credit quality
Loans and leases	59,123	29,811
Commercial and Industrial | Doubtful
Credit quality
Loans and leases	1,367	1,766
Commercial Real Estate
Credit quality
Loans and leases	2,625,688	2,343,495
Commercial Real Estate | Pass
Credit quality
Loans and leases	2,581,682	2,298,839
Commercial Real Estate | Special mention
Credit quality
Loans and leases	23,040	23,859
Commercial Real Estate | Substandard
Credit quality
Loans and leases	20,966	20,797
Construction
Credit quality
Loans and leases	598,763	450,012
Construction | Pass
Credit quality
Loans and leases	591,824	445,149
Construction | Special mention
Credit quality
Loans and leases	6,292	3,789
Construction | Substandard
Credit quality
Loans and leases	647	1,074
Lease Financing
Credit quality
Loans and leases	171,373	180,040
Lease Financing | Pass
Credit quality
Loans and leases	170,673	179,345
Lease Financing | Special mention
Credit quality
Loans and leases	553	368
Lease Financing | Substandard
Credit quality
Loans and leases	147	174
Lease Financing | Doubtful
Credit quality
Loans and leases		153
Residential and consumer
Credit quality
Loans and leases	5,563,650	5,307,231
Residential and consumer | Performing
Credit quality
Loans and leases	5,528,440	5,265,885
Residential and consumer | Non-performing and delinquent
Credit quality
Loans and leases	35,210	41,346
Residential
Credit quality
Loans and leases	4,001,478	3,796,459
Residential | Performing
Credit quality
Loans and leases	3,990,063	3,778,070
Residential | Non-performing and delinquent
Credit quality
Loans and leases	11,415	18,389
Consumer
Credit quality
Loans and leases	1,562,172	1,510,772
Consumer loans | Consumer
Credit quality
Loans and leases	236,304	243,512
Consumer loans | Consumer | Performing
Credit quality
Loans and leases	232,541	240,185
Consumer loans | Consumer | Non-performing and delinquent
Credit quality
Loans and leases	3,763	3,327
Consumer - Auto | Consumer
Credit quality
Loans and leases	1,000,694	922,756
Consumer - Auto | Consumer | Performing
Credit quality
Loans and leases	984,114	906,829
Consumer - Auto | Consumer | Non-performing and delinquent
Credit quality
Loans and leases	16,580	15,927
Credit Cards | Consumer
Credit quality
Loans and leases	325,174	344,504
Credit Cards | Consumer | Performing
Credit quality
Loans and leases	321,722	340,801
Credit Cards | Consumer | Non-performing and delinquent
Credit quality
Loans and leases	$ 3,452	$ 3,703