Loans and Leases and the Allowance for Loan and Lease Losses (Credit Quality Indicators & Narrative) (Details 3) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018
Recorded Investment in Loans and Leases by Class and by Credit Quality Indicator
Total Recorded Investment in Loans and Leases	$ 10,881,298	$ 10,448,774	$ 10,231,062
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	6 months
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
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
Number of days past due for loans and leases in classified credit quality indicator	90 days
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	$ 4,156,733	3,979,792	3,900,308
Commercial | Pass
Recorded Investment in Loans and Leases by Class and by Credit Quality Indicator
Total Recorded Investment in Loans and Leases	4,030,039	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	60,626	48,161
Commercial | Classified
Recorded Investment in Loans and Leases by Class and by Credit Quality Indicator
Total Recorded Investment in Loans and Leases	66,068	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	1,361,011	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	1,305,019	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	19,394	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	36,598	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	2,477,296	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	2,413,316	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	37,454	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	26,526	15,760
Commercial | Construction
Recorded Investment in Loans and Leases by Class and by Credit Quality Indicator
Total Recorded Investment in Loans and Leases	154,754	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	149,757	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	3,778	0
Commercial | Construction | Classified
Recorded Investment in Loans and Leases by Class and by Credit Quality Indicator
Total Recorded Investment in Loans and Leases	1,219	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	163,672	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	161,947	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	1,725	998
Consumer
Recorded Investment in Loans and Leases by Class and by Credit Quality Indicator
Total Recorded Investment in Loans and Leases	6,724,565	6,468,982	$ 6,330,754
Consumer | Pass
Recorded Investment in Loans and Leases by Class and by Credit Quality Indicator
Total Recorded Investment in Loans and Leases	$ 6,715,196	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	$ 9,369	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	3,846,511	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	3,841,820	3,668,475
Consumer | Residential Mortgage | Classified
Recorded Investment in Loans and Leases by Class and by Credit Quality Indicator
Total Recorded Investment in Loans and Leases	4,691	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	1,681,951	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	1,678,930	1,677,193
Consumer | Home Equity | Classified
Recorded Investment in Loans and Leases by Class and by Credit Quality Indicator
Total Recorded Investment in Loans and Leases	3,021	4,249
Consumer | Automobile
Recorded Investment in Loans and Leases by Class and by Credit Quality Indicator
Total Recorded Investment in Loans and Leases	713,424	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	712,842	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	582	513
Consumer | Other
Recorded Investment in Loans and Leases by Class and by Credit Quality Indicator
Total Recorded Investment in Loans and Leases	482,679	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	481,604	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	$ 1,075	$ 914