Loans and Leases and the Allowance for Loan and Lease Losses (Aging Analysis) (Details 4) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Non-Accrual	$ 11,889	$ 15,080
Total Past Due and Non-Accrual	54,609	61,352
Current	10,176,453	9,735,595
Total Loans and Leases	10,231,062	9,796,947	$ 9,573,956
Non-Accrual Loans and Leases that are Current	$ 2,417	2,896
Number of days non-accrual loans are not past due	30 days
30 - 59 Days Past Due
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	$ 26,657	29,465
60 - 89 Days Past Due
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	7,969	9,660
Past Due 90 Days or More
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	8,094	7,147
Commercial
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Non-Accrual	1,857	1,846
Total Past Due and Non-Accrual	8,054	7,274
Current	3,892,254	3,759,224
Total Loans and Leases	3,900,308	3,766,498	3,739,963
Non-Accrual Loans and Leases that are Current	860	778
Commercial | 30 - 59 Days Past Due
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	5,579	4,383
Commercial | 60 - 89 Days Past Due
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	618	1,045
Commercial | Past Due 90 Days or More
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	0	0
Commercial | Commercial and Industrial
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Non-Accrual	1,205	448
Total Past Due and Non-Accrual	5,330	5,285
Current	1,309,279	1,274,062
Total Loans and Leases	1,314,609	1,279,347
Non-Accrual Loans and Leases that are Current	860	313
Commercial | Commercial and Industrial | 30 - 59 Days Past Due
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	4,092	4,196
Commercial | Commercial and Industrial | 60 - 89 Days Past Due
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	33	641
Commercial | Commercial and Industrial | Past Due 90 Days or More
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	0	0
Commercial | Commercial Mortgage
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Non-Accrual	652	1,398
Total Past Due and Non-Accrual	2,724	1,989
Current	2,234,296	2,101,978
Total Loans and Leases	2,237,020	2,103,967
Non-Accrual Loans and Leases that are Current	0	465
Commercial | Commercial Mortgage | 30 - 59 Days Past Due
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	1,487	187
Commercial | Commercial Mortgage | 60 - 89 Days Past Due
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	585	404
Commercial | Commercial Mortgage | Past Due 90 Days or More
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	0	0
Commercial | Construction
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Non-Accrual	0	0
Total Past Due and Non-Accrual	0	0
Current	176,447	202,253
Total Loans and Leases	176,447	202,253
Non-Accrual Loans and Leases that are Current	0	0
Commercial | Construction | 30 - 59 Days Past Due
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	0	0
Commercial | Construction | 60 - 89 Days Past Due
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	0	0
Commercial | Construction | Past Due 90 Days or More
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	0	0
Commercial | Lease Financing
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Non-Accrual	0	0
Total Past Due and Non-Accrual	0	0
Current	172,232	180,931
Total Loans and Leases	172,232	180,931
Non-Accrual Loans and Leases that are Current	0	0
Commercial | Lease Financing | 30 - 59 Days Past Due
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	0	0
Commercial | Lease Financing | 60 - 89 Days Past Due
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	0	0
Commercial | Lease Financing | Past Due 90 Days or More
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	0	0
Consumer
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Non-Accrual	10,032	13,234
Total Past Due and Non-Accrual	46,555	54,078
Current	6,284,199	5,976,371
Total Loans and Leases	6,330,754	6,030,449	$ 5,833,993
Non-Accrual Loans and Leases that are Current	1,557	2,118
Consumer | 30 - 59 Days Past Due
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	21,078	25,082
Consumer | 60 - 89 Days Past Due
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	7,351	8,615
Consumer | Past Due 90 Days or More
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	8,094	7,147
Consumer | Residential Mortgage
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Non-Accrual	6,359	9,243
Total Past Due and Non-Accrual	13,729	21,769
Current	3,582,898	3,445,004
Total Loans and Leases	3,596,627	3,466,773
Non-Accrual Loans and Leases that are Current	709	806
Consumer | Residential Mortgage | 30 - 59 Days Past Due
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	2,335	7,815
Consumer | Residential Mortgage | 60 - 89 Days Past Due
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	2,609	2,008
Consumer | Residential Mortgage | Past Due 90 Days or More
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	2,426	2,703
Consumer | Home Equity
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Non-Accrual	3,673	3,991
Total Past Due and Non-Accrual	10,971	10,883
Current	1,614,237	1,574,572
Total Loans and Leases	1,625,208	1,585,455
Non-Accrual Loans and Leases that are Current	848	1,312
Consumer | Home Equity | 30 - 59 Days Past Due
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	3,276	2,532
Consumer | Home Equity | 60 - 89 Days Past Due
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	910	2,736
Consumer | Home Equity | Past Due 90 Days or More
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	3,112	1,624
Consumer | Automobile
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Non-Accrual	0	0
Total Past Due and Non-Accrual	15,927	14,846
Current	609,159	513,628
Total Loans and Leases	625,086	528,474
Non-Accrual Loans and Leases that are Current	0	0
Consumer | Automobile | 30 - 59 Days Past Due
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	12,756	11,728
Consumer | Automobile | 60 - 89 Days Past Due
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	2,342	2,232
Consumer | Automobile | Past Due 90 Days or More
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	829	886
Consumer | Other
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Non-Accrual	0	0
Total Past Due and Non-Accrual	5,928	6,580
Current	477,905	443,167
Total Loans and Leases	483,833	449,747
Non-Accrual Loans and Leases that are Current	0	0
Consumer | Other | 30 - 59 Days Past Due
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	2,711	3,007
Consumer | Other | 60 - 89 Days Past Due
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	1,490	1,639
Consumer | Other | Past Due 90 Days or More
Aging Analysis of Accruing and Non-Accruing Loans and Leases
Days Past Due	$ 1,727	$ 1,934