Loans and Leases and the Allowance for Loan and Lease Losses (Credit Quality Indicators & Narrative) (Details 3) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Recorded investment in loans and leases by class and by credit quality indicator
Total Recorded Investment in Loans and Leases	$ 10,990,892	$ 10,448,774	$ 9,796,947
Classified
Recorded investment in loans and leases by class and by credit quality indicator
Number of months up to which residential and home equity loans may be considered classified, even if they are current as to principal and interest (in months)	6 months
Residential Mortgage | Classified
Recorded investment in loans and leases by class and by credit quality indicator
Maximum current loan-to-value ratio for residential mortgage and home equity loans to be considered as pass (as a percent)	60.00%
Home Equity | Classified
Recorded investment in loans and leases by class and by credit quality indicator
Maximum current loan-to-value ratio for residential mortgage and home equity loans to be considered as pass (as a percent)	60.00%
Commercial
Recorded investment in loans and leases by class and by credit quality indicator
Total Recorded Investment in Loans and Leases	$ 4,213,827	3,979,792	3,766,498
Commercial | Pass
Recorded investment in loans and leases by class and by credit quality indicator
Total Recorded Investment in Loans and Leases	4,079,663	3,902,369
Commercial | Special Mention
Recorded investment in loans and leases by class and by credit quality indicator
Total Recorded Investment in Loans and Leases	58,323	48,161
Commercial | Classified
Recorded investment in loans and leases by class and by credit quality indicator
Total Recorded Investment in Loans and Leases	75,841	29,262
Commercial | Commercial and Industrial
Recorded investment in loans and leases by class and by credit quality indicator
Total Recorded Investment in Loans and Leases	1,379,152	1,331,149
Commercial | Commercial and Industrial | Pass
Recorded investment in loans and leases by class and by credit quality indicator
Total Recorded Investment in Loans and Leases	1,306,040	1,302,278
Commercial | Commercial and Industrial | Special Mention
Recorded investment in loans and leases by class and by credit quality indicator
Total Recorded Investment in Loans and Leases	37,722	17,688
Commercial | Commercial and Industrial | Classified
Recorded investment in loans and leases by class and by credit quality indicator
Total Recorded Investment in Loans and Leases	35,390	11,183
Commercial | Commercial Mortgage
Recorded investment in loans and leases by class and by credit quality indicator
Total Recorded Investment in Loans and Leases	2,518,051	2,302,356
Commercial | Commercial Mortgage | Pass
Recorded investment in loans and leases by class and by credit quality indicator
Total Recorded Investment in Loans and Leases	2,463,858	2,256,128
Commercial | Commercial Mortgage | Special Mention
Recorded investment in loans and leases by class and by credit quality indicator
Total Recorded Investment in Loans and Leases	16,453	30,468
Commercial | Commercial Mortgage | Classified
Recorded investment in loans and leases by class and by credit quality indicator
Total Recorded Investment in Loans and Leases	37,740	15,760
Commercial | Construction
Recorded investment in loans and leases by class and by credit quality indicator
Total Recorded Investment in Loans and Leases	194,170	170,061
Commercial | Construction | Pass
Recorded investment in loans and leases by class and by credit quality indicator
Total Recorded Investment in Loans and Leases	188,832	168,740
Commercial | Construction | Special Mention
Recorded investment in loans and leases by class and by credit quality indicator
Total Recorded Investment in Loans and Leases	4,148	0
Commercial | Construction | Classified
Recorded investment in loans and leases by class and by credit quality indicator
Total Recorded Investment in Loans and Leases	1,190	1,321
Commercial | Lease Financing
Recorded investment in loans and leases by class and by credit quality indicator
Total Recorded Investment in Loans and Leases	122,454	176,226
Commercial | Lease Financing | Pass
Recorded investment in loans and leases by class and by credit quality indicator
Total Recorded Investment in Loans and Leases	120,933	175,223
Commercial | Lease Financing | Special Mention
Recorded investment in loans and leases by class and by credit quality indicator
Total Recorded Investment in Loans and Leases	0	5
Commercial | Lease Financing | Classified
Recorded investment in loans and leases by class and by credit quality indicator
Total Recorded Investment in Loans and Leases	1,521	998
Consumer
Recorded investment in loans and leases by class and by credit quality indicator
Total Recorded Investment in Loans and Leases	6,777,065	6,468,982	$ 6,030,449
Consumer | Pass
Recorded investment in loans and leases by class and by credit quality indicator
Total Recorded Investment in Loans and Leases	$ 6,765,307	6,457,985
Consumer | Classified
Recorded investment in loans and leases by class and by credit quality indicator
Number of days past due for loans and leases in classified credit quality indicator	90 days
Total Recorded Investment in Loans and Leases	$ 11,758	10,997
Consumer | Residential Mortgage
Recorded investment in loans and leases by class and by credit quality indicator
Total Recorded Investment in Loans and Leases	3,891,100	3,673,796
Consumer | Residential Mortgage | Pass
Recorded investment in loans and leases by class and by credit quality indicator
Total Recorded Investment in Loans and Leases	$ 3,886,389	3,668,475
Consumer | Residential Mortgage | Classified
Recorded investment in loans and leases by class and by credit quality indicator
Number of days past due for loans and leases in classified credit quality indicator	90 days
Total Recorded Investment in Loans and Leases	$ 4,711	5,321
Consumer | Home Equity
Recorded investment in loans and leases by class and by credit quality indicator
Total Recorded Investment in Loans and Leases	1,676,073	1,681,442
Consumer | Home Equity | Pass
Recorded investment in loans and leases by class and by credit quality indicator
Total Recorded Investment in Loans and Leases	$ 1,671,468	1,677,193
Consumer | Home Equity | Classified
Recorded investment in loans and leases by class and by credit quality indicator
Number of days past due for loans and leases in classified credit quality indicator	90 days
Total Recorded Investment in Loans and Leases	$ 4,605	4,249
Consumer | Automobile
Recorded investment in loans and leases by class and by credit quality indicator
Total Recorded Investment in Loans and Leases	720,286	658,133
Consumer | Automobile | Pass
Recorded investment in loans and leases by class and by credit quality indicator
Total Recorded Investment in Loans and Leases	719,337	657,620
Consumer | Automobile | Classified
Recorded investment in loans and leases by class and by credit quality indicator
Total Recorded Investment in Loans and Leases	949	513
Consumer | Other
Recorded investment in loans and leases by class and by credit quality indicator
Total Recorded Investment in Loans and Leases	489,606	455,611
Consumer | Other | Pass
Recorded investment in loans and leases by class and by credit quality indicator
Total Recorded Investment in Loans and Leases	488,113	454,697
Consumer | Other | Classified
Recorded investment in loans and leases by class and by credit quality indicator
Total Recorded Investment in Loans and Leases	$ 1,493	$ 914