Allowance for Loan and Lease Losses - Aging of Analysis of Past Due Loans and Leases (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment, Past Due
Total Past Due	$ 58,614	$ 45,575
Current	13,011,034	12,221,969
Total Accruing Loans and Leases	13,069,648	12,267,544
Total NonAccruing Loans and Leases	6,543	9,825
Total loans and leases	13,076,191	12,277,369	$ 11,520,378
30 - 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	41,727	32,998
60 - 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	10,499	8,203
Greater Than or Equal to 90 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	6,388	4,374
Commercial and Industrial
Financing Receivable, Recorded Investment, Past Due
Total Past Due	1,434	376
Current	3,207,052	3,131,958
Total Accruing Loans and Leases	3,208,486	3,132,334
Total NonAccruing Loans and Leases	274	2,932
Total loans and leases	3,208,760	3,135,266	3,239,600
Commercial and Industrial | 30 - 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	1,293	156
Commercial and Industrial | Greater Than or Equal to 90 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	141	220
Commercial Real Estate
Financing Receivable, Recorded Investment, Past Due
Total Past Due		2,499
Current	2,989,125	2,663,312
Total Accruing Loans and Leases	2,989,125	2,665,811
Total NonAccruing Loans and Leases	1,658	1,786
Total loans and leases	2,990,783	2,667,597	2,343,495
Commercial Real Estate | 60 - 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due		1,099
Commercial Real Estate | Greater Than or Equal to 90 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due		1,400
Construction
Financing Receivable, Recorded Investment, Past Due
Total Past Due	91	2,001
Current	626,666	630,910
Total Accruing Loans and Leases	626,757	632,911
Total loans and leases	626,757	632,911	450,012
Construction | 30 - 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	91
Construction | 60 - 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due		2,001
Lease Financing
Financing Receivable, Recorded Investment, Past Due
Total Past Due	47
Current	147,722	165,066
Total Accruing Loans and Leases	147,769	165,066
Total loans and leases	147,769	165,066	180,040
Lease Financing | 30 - 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	47
Residential
Financing Receivable, Recorded Investment, Past Due
Total Past Due	3,318	6,165
Current	3,519,172	3,215,329
Total Accruing Loans and Leases	3,522,490	3,221,494
Total NonAccruing Loans and Leases	4,611	5,107
Total loans and leases	4,439,618	4,090,053	3,796,459
Total Outstanding, Residential mortgage	3,527,101	3,226,601
Residential | 30 - 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	2,274	5,340
Residential | 60 - 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	1,012	825
Residential | Greater Than or Equal to 90 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	32
Home Equity Line
Financing Receivable, Recorded Investment, Past Due
Total Past Due	9,233	4,947
Current	903,284	858,505
Total Accruing Loans and Leases	912,517	863,452
Total loans and leases	912,517	863,452
Home Equity Line | 30 - 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	5,616	3,123
Home Equity Line | 60 - 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	775	464
Home Equity Line | Greater Than or Equal to 90 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	2,842	1,360
Consumer
Financing Receivable, Recorded Investment, Past Due
Total Past Due	44,491	29,587
Current	1,618,013	1,556,889
Total Accruing Loans and Leases	1,662,504	1,586,476
Total loans and leases	1,662,504	1,586,476	$ 1,510,772
Consumer | 30 - 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	32,406	24,379
Consumer | 60 - 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	8,712	3,814
Consumer | Greater Than or Equal to 90 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	$ 3,373	$ 1,394