Allowance for Loan and Lease Losses - Aging of Analysis of Past Due Loans and Leases (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Financing Receivable, Recorded Investment, Past Due
Total Past Due	$ 46,282	$ 58,614
Current	13,146,892	13,011,034
Total Accruing Loans and Leases	13,193,174	13,069,648
Total Non Accruing Loans and Leases	4,280	6,543
Total loans and leases	13,197,454	13,076,191
30 - 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	31,716	41,727
60 - 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	8,141	10,499
Greater Than or Equal to 90 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	6,425	6,388
Commercial and Industrial
Financing Receivable, Recorded Investment, Past Due
Total Past Due	2,072	1,434
Current	3,201,508	3,207,052
Total Accruing Loans and Leases	3,203,580	3,208,486
Total Non Accruing Loans and Leases	190	274
Total loans and leases	3,203,770	3,208,760
Commercial and Industrial | 30 - 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	1,415	1,293
Commercial and Industrial | 60 - 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	307
Commercial and Industrial | Greater Than or Equal to 90 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	350	141
Commercial Real Estate
Financing Receivable, Recorded Investment, Past Due
Total Past Due	354
Current	3,146,950	2,989,125
Total Accruing Loans and Leases	3,147,304	2,989,125
Total Non Accruing Loans and Leases		1,658
Total loans and leases	3,147,304	2,990,783
Commercial Real Estate | 30 - 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	225
Commercial Real Estate | 60 - 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	129
Construction
Financing Receivable, Recorded Investment, Past Due
Total Past Due	89	91
Current	595,402	626,666
Total Accruing Loans and Leases	595,491	626,757
Total loans and leases	595,491	626,757
Construction | 30 - 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due		91
Construction | Greater Than or Equal to 90 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	89
Lease Financing
Financing Receivable, Recorded Investment, Past Due
Total Past Due		47
Current	145,987	147,722
Total Accruing Loans and Leases	145,987	147,769
Total loans and leases	145,987	147,769
Lease Financing | 30 - 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due		47
Residential Mortgage
Financing Receivable, Recorded Investment, Past Due
Total Past Due	1,752	3,318
Current	3,538,122	3,519,172
Total Accruing Loans and Leases	3,539,874	3,522,490
Total Non Accruing Loans and Leases	4,090	4,611
Total loans and leases	3,543,964	3,527,101
Residential Mortgage | 30 - 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	1,353	2,274
Residential Mortgage | 60 - 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	399	1,012
Residential Mortgage | 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	6,008	9,233
Current	901,821	903,284
Total Accruing Loans and Leases	907,829	912,517
Total loans and leases	907,829	912,517
Home Equity Line | 30 - 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	3,083	5,616
Home Equity Line | 60 - 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	477	775
Home Equity Line | Greater Than or Equal to 90 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	2,448	2,842
Consumer
Financing Receivable, Recorded Investment, Past Due
Total Past Due	36,007	44,491
Current	1,617,102	1,618,013
Total Accruing Loans and Leases	1,653,109	1,662,504
Total loans and leases	1,653,109	1,662,504
Consumer | 30 - 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	25,640	32,406
Consumer | 60 - 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	6,829	8,712
Consumer | Greater Than or Equal to 90 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	$ 3,538	$ 3,373