Allowance for Loan and Lease Losses - Aging of Analysis of Past Due Loans and Leases (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment, Past Due
Total Past Due	$ 36,485	$ 45,575
Current	12,587,757	12,221,969
Total Accruing Loans and Leases	12,624,242	12,267,544
Total NonAccruing Loans and Leases	13,444	9,825
Total loans and leases	12,637,686	12,277,369
30 - 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	28,168	32,998
60 - 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	5,122	8,203
Greater Than or Equal to 90 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	3,195	4,374
Commercial and Industrial
Financing Receivable, Recorded Investment, Past Due
Total Past Due	1,279	376
Current	3,113,045	3,131,958
Total Accruing Loans and Leases	3,114,324	3,132,334
Total NonAccruing Loans and Leases	1,821	2,932
Total loans and leases	3,116,145	3,135,266
Commercial and Industrial | 30 - 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	495	156
Commercial and Industrial | 60 - 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	621
Commercial and Industrial | Greater Than or Equal to 90 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	163	220
Commercial Real Estate
Financing Receivable, Recorded Investment, Past Due
Total Past Due	747	2,499
Current	2,833,929	2,663,312
Total Accruing Loans and Leases	2,834,676	2,665,811
Total NonAccruing Loans and Leases	2,844	1,786
Total loans and leases	2,837,520	2,667,597
Commercial Real Estate | 30 - 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	567
Commercial Real Estate | 60 - 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	180	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		2,001
Current	651,846	630,910
Total Accruing Loans and Leases	651,846	632,911
Total NonAccruing Loans and Leases	2,238
Total loans and leases	654,084	632,911
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
Current	161,766	165,066
Total Accruing Loans and Leases	161,766	165,066
Total loans and leases	161,766	165,066
Residential
Financing Receivable, Recorded Investment, Past Due
Total Past Due	7,972	11,112
Current	4,221,570	4,073,834
Total Accruing Loans and Leases	4,229,542	4,084,946
Total NonAccruing Loans and Leases	6,541	5,107
Total loans and leases	4,236,083	4,090,053
Residential | 30 - 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	5,607	8,463
Residential | 60 - 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	784	1,289
Residential | Greater Than or Equal to 90 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	1,581	1,360
Consumer
Financing Receivable, Recorded Investment, Past Due
Total Past Due	26,487	29,587
Current	1,605,601	1,556,889
Total Accruing Loans and Leases	1,632,088	1,586,476
Total loans and leases	1,632,088	1,586,476
Consumer | 30 - 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	21,499	24,379
Consumer | 60 - 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	3,537	3,814
Consumer | Greater Than or Equal to 90 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	$ 1,451	$ 1,394