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, 2015	Dec. 31, 2014	Sep. 30, 2014
Recorded Investment in Loans and Leases by Class and by Credit Quality Indicator
Total Recorded Investment in Loans and Leases	$ 7,689,772	$ 6,897,589	$ 6,606,350
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	$ 3,123,245	2,828,128	2,728,924
Commercial | Pass
Recorded Investment in Loans and Leases by Class and by Credit Quality Indicator
Total Recorded Investment in Loans and Leases	3,002,627	2,693,450
Commercial | Special Mention
Recorded Investment in Loans and Leases by Class and by Credit Quality Indicator
Total Recorded Investment in Loans and Leases	52,044	62,463
Commercial | Classified
Recorded Investment in Loans and Leases by Class and by Credit Quality Indicator
Total Recorded Investment in Loans and Leases	68,574	72,215
Commercial | Commercial and Industrial
Recorded Investment in Loans and Leases by Class and by Credit Quality Indicator
Total Recorded Investment in Loans and Leases	1,169,817	1,055,243
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	1,122,454	1,001,474
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	20,726	17,364
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	26,637	36,405
Commercial | Commercial Mortgage
Recorded Investment in Loans and Leases by Class and by Credit Quality Indicator
Total Recorded Investment in Loans and Leases	1,622,119	1,437,513
Commercial | Commercial Mortgage | Pass
Recorded Investment in Loans and Leases by Class and by Credit Quality Indicator
Total Recorded Investment in Loans and Leases	1,551,159	1,358,812
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	31,145	45,082
Commercial | Commercial Mortgage | Classified
Recorded Investment in Loans and Leases by Class and by Credit Quality Indicator
Total Recorded Investment in Loans and Leases	39,815	33,619
Commercial | Construction
Recorded Investment in Loans and Leases by Class and by Credit Quality Indicator
Total Recorded Investment in Loans and Leases	129,254	109,183
Commercial | Construction | Pass
Recorded Investment in Loans and Leases by Class and by Credit Quality Indicator
Total Recorded Investment in Loans and Leases	127,541	107,381
Commercial | Construction | Special Mention
Recorded Investment in Loans and Leases by Class and by Credit Quality Indicator
Total Recorded Investment in Loans and Leases	88	0
Commercial | Construction | Classified
Recorded Investment in Loans and Leases by Class and by Credit Quality Indicator
Total Recorded Investment in Loans and Leases	1,625	1,802
Commercial | Lease Financing
Recorded Investment in Loans and Leases by Class and by Credit Quality Indicator
Total Recorded Investment in Loans and Leases	202,055	226,189
Commercial | Lease Financing | Pass
Recorded Investment in Loans and Leases by Class and by Credit Quality Indicator
Total Recorded Investment in Loans and Leases	201,473	225,783
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	85	17
Commercial | Lease Financing | Classified
Recorded Investment in Loans and Leases by Class and by Credit Quality Indicator
Total Recorded Investment in Loans and Leases	497	389
Consumer
Recorded Investment in Loans and Leases by Class and by Credit Quality Indicator
Total Recorded Investment in Loans and Leases	4,566,527	4,069,461	$ 3,877,426
Consumer | Pass
Recorded Investment in Loans and Leases by Class and by Credit Quality Indicator
Total Recorded Investment in Loans and Leases	$ 4,544,753	4,048,753
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	$ 21,774	20,708
Consumer | Residential Mortgage
Recorded Investment in Loans and Leases by Class and by Credit Quality Indicator
Total Recorded Investment in Loans and Leases	2,875,605	2,571,090
Consumer | Residential Mortgage | Pass
Recorded Investment in Loans and Leases by Class and by Credit Quality Indicator
Total Recorded Investment in Loans and Leases	2,859,438	2,556,140
Consumer | Residential Mortgage | Classified
Recorded Investment in Loans and Leases by Class and by Credit Quality Indicator
Total Recorded Investment in Loans and Leases	16,167	14,950
Consumer | Home Equity
Recorded Investment in Loans and Leases by Class and by Credit Quality Indicator
Total Recorded Investment in Loans and Leases	993,817	866,688
Consumer | Home Equity | Pass
Recorded Investment in Loans and Leases by Class and by Credit Quality Indicator
Total Recorded Investment in Loans and Leases	989,433	862,258
Consumer | Home Equity | Classified
Recorded Investment in Loans and Leases by Class and by Credit Quality Indicator
Total Recorded Investment in Loans and Leases	4,384	4,430
Consumer | Automobile
Recorded Investment in Loans and Leases by Class and by Credit Quality Indicator
Total Recorded Investment in Loans and Leases	367,640	323,848
Consumer | Automobile | Pass
Recorded Investment in Loans and Leases by Class and by Credit Quality Indicator
Total Recorded Investment in Loans and Leases	367,009	323,232
Consumer | Automobile | Classified
Recorded Investment in Loans and Leases by Class and by Credit Quality Indicator
Total Recorded Investment in Loans and Leases	631	616
Consumer | Other
Recorded Investment in Loans and Leases by Class and by Credit Quality Indicator
Total Recorded Investment in Loans and Leases	329,465	307,835
Consumer | Other | Pass
Recorded Investment in Loans and Leases by Class and by Credit Quality Indicator
Total Recorded Investment in Loans and Leases	328,873	307,123
Consumer | Other | Classified
Recorded Investment in Loans and Leases by Class and by Credit Quality Indicator
Total Recorded Investment in Loans and Leases	$ 592	$ 712