Allowance for Loan and Lease Losses - Aging of Analysis of Past Due Loans and Leases (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment, Past Due
Total Past Due	$ 56,576	$ 45,575
Current	12,532,942	12,221,969
Total Accruing Loans and Leases	12,589,518	12,267,544
Total NonAccruing Loans and Leases	10,946	9,825
Total loans and leases	12,600,464	12,277,369
30 - 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	42,470	32,998
60 - 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	8,192	8,203
Greater Than or Equal to 90 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	5,914	4,374
Commercial and Industrial
Financing Receivable, Recorded Investment, Past Due
Total Past Due	3,269	376
Current	2,965,487	3,131,958
Total Accruing Loans and Leases	2,968,756	3,132,334
Total NonAccruing Loans and Leases	481	2,932
Total loans and leases	2,969,237	3,135,266
Commercial and Industrial | 30 - 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	2,911	156
Commercial and Industrial | 60 - 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	217
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	913	2,499
Current	2,888,054	2,663,312
Total Accruing Loans and Leases	2,888,967	2,665,811
Total NonAccruing Loans and Leases	2,786	1,786
Total loans and leases	2,891,753	2,667,597
Commercial Real Estate | 30 - 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	457
Commercial Real Estate | 60 - 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	284	1,099
Commercial Real Estate | Greater Than or Equal to 90 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	172	1,400
Construction
Financing Receivable, Recorded Investment, Past Due
Total Past Due	232	2,001
Current	610,561	630,910
Total Accruing Loans and Leases	610,793	632,911
Total NonAccruing Loans and Leases	2,001
Total loans and leases	612,794	632,911
Construction | 30 - 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	232
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	161,314	165,066
Total Accruing Loans and Leases	161,314	165,066
Total loans and leases	161,314	165,066
Residential
Financing Receivable, Recorded Investment, Past Due
Total Past Due	9,893	11,112
Current	4,297,918	4,073,834
Total Accruing Loans and Leases	4,307,811	4,084,946
Total NonAccruing Loans and Leases	5,678	5,107
Total loans and leases	4,313,489	4,090,053
Residential | 30 - 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	5,927	8,463
Residential | 60 - 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	1,178	1,289
Residential | Greater Than or Equal to 90 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	2,788	1,360
Consumer
Financing Receivable, Recorded Investment, Past Due
Total Past Due	42,269	29,587
Current	1,609,608	1,556,889
Total Accruing Loans and Leases	1,651,877	1,586,476
Total loans and leases	1,651,877	1,586,476
Consumer | 30 - 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	32,943	24,379
Consumer | 60 - 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	6,513	3,814
Consumer | Greater Than or Equal to 90 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	$ 2,813	$ 1,394