Loans and Leases and the Allowance for Loan and Lease Losses (Credit Quality Indicators & Narrative) (Details 3) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Financing Receivable, Credit Quality Indicator [Line Items]
Total Recorded Investment in Loans and Leases	$ 11,352,780	$ 10,990,892
Classified
Financing Receivable, Credit Quality Indicator [Line Items]
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
Financing Receivable, Credit Quality Indicator [Line Items]
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
Financing Receivable, Credit Quality Indicator [Line Items]
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
Financing Receivable, Credit Quality Indicator [Line Items]
Total Recorded Investment in Loans and Leases	$ 4,530,569	4,213,827
Commercial | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Total Recorded Investment in Loans and Leases		4,079,663
Commercial | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Total Recorded Investment in Loans and Leases		58,323
Commercial | Classified
Financing Receivable, Credit Quality Indicator [Line Items]
Total Recorded Investment in Loans and Leases		75,841
Commercial | Commercial and Industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Total Recorded Investment in Loans and Leases	1,558,232	1,379,152
Commercial | Commercial and Industrial | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Total Recorded Investment in Loans and Leases		1,306,040
Commercial | Commercial and Industrial | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Total Recorded Investment in Loans and Leases		37,722
Commercial | Commercial and Industrial | Classified
Financing Receivable, Credit Quality Indicator [Line Items]
Total Recorded Investment in Loans and Leases		35,390
Commercial | Commercial Mortgage
Financing Receivable, Credit Quality Indicator [Line Items]
Total Recorded Investment in Loans and Leases	2,616,243	2,518,051
Commercial | Commercial Mortgage | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Total Recorded Investment in Loans and Leases		2,463,858
Commercial | Commercial Mortgage | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Total Recorded Investment in Loans and Leases		16,453
Commercial | Commercial Mortgage | Classified
Financing Receivable, Credit Quality Indicator [Line Items]
Total Recorded Investment in Loans and Leases		37,740
Commercial | Construction
Financing Receivable, Credit Quality Indicator [Line Items]
Total Recorded Investment in Loans and Leases	245,390	194,170
Commercial | Construction | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Total Recorded Investment in Loans and Leases		188,832
Commercial | Construction | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Total Recorded Investment in Loans and Leases		4,148
Commercial | Construction | Classified
Financing Receivable, Credit Quality Indicator [Line Items]
Total Recorded Investment in Loans and Leases		1,190
Commercial | Lease Financing
Financing Receivable, Credit Quality Indicator [Line Items]
Total Recorded Investment in Loans and Leases	110,704	122,454
Commercial | Lease Financing | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Total Recorded Investment in Loans and Leases		120,933
Commercial | Lease Financing | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Total Recorded Investment in Loans and Leases		0
Commercial | Lease Financing | Classified
Financing Receivable, Credit Quality Indicator [Line Items]
Total Recorded Investment in Loans and Leases		1,521
Consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Total Recorded Investment in Loans and Leases	$ 6,822,211	6,777,065
Consumer | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Total Recorded Investment in Loans and Leases		6,765,307
Consumer | Classified
Financing Receivable, Credit Quality Indicator [Line Items]
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
Consumer | Residential Mortgage
Financing Receivable, Credit Quality Indicator [Line Items]
Total Recorded Investment in Loans and Leases	$ 3,928,183	3,891,100
Consumer | Residential Mortgage | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Total Recorded Investment in Loans and Leases		3,886,389
Consumer | Residential Mortgage | Classified
Financing Receivable, Credit Quality Indicator [Line Items]
Total Recorded Investment in Loans and Leases		4,711
Consumer | Home Equity
Financing Receivable, Credit Quality Indicator [Line Items]
Total Recorded Investment in Loans and Leases	1,692,154	1,676,073
Consumer | Home Equity | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Total Recorded Investment in Loans and Leases		1,671,468
Consumer | Home Equity | Classified
Financing Receivable, Credit Quality Indicator [Line Items]
Total Recorded Investment in Loans and Leases		4,605
Consumer | Automobile
Financing Receivable, Credit Quality Indicator [Line Items]
Total Recorded Investment in Loans and Leases	716,214	720,286
Consumer | Automobile | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Total Recorded Investment in Loans and Leases		719,337
Consumer | Automobile | Classified
Financing Receivable, Credit Quality Indicator [Line Items]
Total Recorded Investment in Loans and Leases		949
Consumer | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Total Recorded Investment in Loans and Leases	$ 485,660	489,606
Consumer | Other | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Total Recorded Investment in Loans and Leases		488,113
Consumer | Other | Classified
Financing Receivable, Credit Quality Indicator [Line Items]
Total Recorded Investment in Loans and Leases		$ 1,493