Allowance for Loan and Lease Losses - Aging of Analysis of Past Due Loans and Leases (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment, Past Due
Total Past Due	$ 34,723	$ 45,575
Current	12,417,319	12,221,969
Total Accruing Loans and Leases	12,452,042	12,267,544
Total NonAccruing Loans and Leases	12,123	9,825
Total loans and leases	12,464,165	12,277,369
30 - 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	25,250	32,998
60 - 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	5,834	8,203
Greater Than or Equal to 90 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	3,639	4,374
Commercial and Industrial
Financing Receivable, Recorded Investment, Past Due
Total Past Due	366	376
Current	3,216,956	3,131,958
Total Accruing Loans and Leases	3,217,322	3,132,334
Total NonAccruing Loans and Leases	1,888	2,932
Total loans and leases	3,219,210	3,135,266
Commercial and Industrial | 30 - 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	253	156
Commercial and Industrial | 60 - 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	30
Commercial and Industrial | Greater Than or Equal to 90 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	83	220
Commercial Real Estate
Financing Receivable, Recorded Investment, Past Due
Total Past Due	712	2,499
Current	2,734,960	2,663,312
Total Accruing Loans and Leases	2,735,672	2,665,811
Total NonAccruing Loans and Leases	2,885	1,786
Total loans and leases	2,738,557	2,667,597
Commercial Real Estate | 30 - 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	712
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	343	2,001
Current	591,922	630,910
Total Accruing Loans and Leases	592,265	632,911
Total NonAccruing Loans and Leases	2,001
Total loans and leases	594,266	632,911
Construction | 60 - 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due		2,001
Construction | Greater Than or Equal to 90 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	343
Lease Financing
Financing Receivable, Recorded Investment, Past Due
Current	160,140	165,066
Total Accruing Loans and Leases	160,140	165,066
Total loans and leases	160,140	165,066
Residential
Financing Receivable, Recorded Investment, Past Due
Total Past Due	8,453	11,112
Current	4,142,201	4,073,834
Total Accruing Loans and Leases	4,150,654	4,084,946
Total NonAccruing Loans and Leases	5,349	5,107
Total loans and leases	4,156,003	4,090,053
Residential | 30 - 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	4,673	8,463
Residential | 60 - 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	2,311	1,289
Residential | Greater Than or Equal to 90 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	1,469	1,360
Consumer
Financing Receivable, Recorded Investment, Past Due
Total Past Due	24,849	29,587
Current	1,571,140	1,556,889
Total Accruing Loans and Leases	1,595,989	1,586,476
Total loans and leases	1,595,989	1,586,476
Consumer | 30 - 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	19,612	24,379
Consumer | 60 - 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	3,493	3,814
Consumer | Greater Than or Equal to 90 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	$ 1,744	$ 1,394