Allowance for Loan and Lease Losses - Aging of Analysis of Past Due Loans and Leases (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Recorded Investment, Past Due
Total Past Due	$ 45,575	$ 36,688
Current	12,221,969	11,474,260
Total Accruing Loans and Leases	12,267,544	11,510,948
Total NonAccruing Loans and Leases	9,825	9,430
Total loans and leases	12,277,369	11,520,378	$ 10,722,030
30 - 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	32,998	28,728
60 - 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	8,203	4,692
Greater Than or Equal to 90 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	4,374	3,268
Commercial and Industrial
Financing Receivable, Recorded Investment, Past Due
Total Past Due	376	1,332
Current	3,131,958	3,235,538
Total Accruing Loans and Leases	3,132,334	3,236,870
Total NonAccruing Loans and Leases	2,932	2,730
Total loans and leases	3,135,266	3,239,600	3,057,455
Commercial and Industrial | 30 - 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	156	720
Commercial and Industrial | 60 - 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due		163
Commercial and Industrial | Greater Than or Equal to 90 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	220	449
Commercial Real Estate
Financing Receivable, Recorded Investment, Past Due
Total Past Due	2,499	475
Current	2,663,312	2,343,020
Total Accruing Loans and Leases	2,665,811	2,343,495
Total NonAccruing Loans and Leases	1,786
Total loans and leases	2,667,597	2,343,495	2,164,448
Commercial Real Estate | 30 - 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due		475
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	2,001
Current	630,910	450,012
Total Accruing Loans and Leases	632,911	450,012
Total loans and leases	632,911	450,012	367,460
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		83
Current	165,066	179,804
Total Accruing Loans and Leases	165,066	179,887
Total NonAccruing Loans and Leases		153
Total loans and leases	165,066	180,040	198,679
Lease Financing | Greater Than or Equal to 90 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due		83
Residential
Financing Receivable, Recorded Investment, Past Due
Total Past Due	11,112	11,842
Current	4,073,834	3,778,070
Total Accruing Loans and Leases	4,084,946	3,789,912
Total NonAccruing Loans and Leases	5,107	6,547
Total loans and leases	4,090,053	3,796,459	3,532,427
Residential | 30 - 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	8,463	9,907
Residential | 60 - 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	1,289	1,069
Residential | Greater Than or Equal to 90 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	1,360	866
Consumer
Financing Receivable, Recorded Investment, Past Due
Total Past Due	29,587	22,956
Current	1,556,889	1,487,816
Total Accruing Loans and Leases	1,586,476	1,510,772
Total loans and leases	1,586,476	1,510,772	$ 1,401,561
Consumer | 30 - 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	24,379	17,626
Consumer | 60 - 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	3,814	3,460
Consumer | Greater Than or Equal to 90 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	$ 1,394	$ 1,870