Allowance for Loan and Lease Losses - Disaggregation by Impairment Methodology (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014
Allowance for loan and lease losses:
Individually evaluated for impairment	$ 690		$ 592
Collectively evaluated for impairment	135,670		134,892
Total allowance for loan and lease losses	136,360	$ 137,154	135,484	$ 136,338	$ 135,698	$ 134,799
Loans and leases:
Individually evaluated for impairment	64,028		44,147
Collectively evaluated for impairment	11,123,667		10,677,883
Total loans and leases	11,187,695		10,722,030
Commercial Lending
Loans and leases:
Total loans and leases	6,081,082		5,788,042
Commercial and Industrial
Allowance for loan and lease losses:
Individually evaluated for impairment	109
Collectively evaluated for impairment	35,683		34,025
Total allowance for loan and lease losses	35,792	35,027	34,025	32,914	32,228	31,835
Loans and leases:
Individually evaluated for impairment	30,574		15,845
Collectively evaluated for impairment	3,257,929		3,041,610
Total loans and leases	3,288,503		3,057,455
Commercial Real Estate
Allowance for loan and lease losses:
Collectively evaluated for impairment	18,260		18,489
Total allowance for loan and lease losses	18,260	18,504	18,489	15,698	16,508	16,320
Loans and leases:
Individually evaluated for impairment	11,158		5,787
Collectively evaluated for impairment	2,170,574		2,158,661
Total loans and leases	2,181,732		2,164,448
Construction
Allowance for loan and lease losses:
Collectively evaluated for impairment	4,636		3,793
Total allowance for loan and lease losses	4,636	4,514	3,793	3,626	3,654	4,725
Loans and leases:
Collectively evaluated for impairment	424,743		367,460
Total loans and leases	424,743		367,460
Lease Financing
Allowance for loan and lease losses:
Collectively evaluated for impairment	780		888
Total allowance for loan and lease losses	780	807	888	1,008	1,010	1,089
Loans and leases:
Individually evaluated for impairment	173		181
Collectively evaluated for impairment	185,931		198,498
Total loans and leases	186,104		198,679
Residential
Allowance for loan and lease losses:
Individually evaluated for impairment	581		592
Collectively evaluated for impairment	45,871		45,507
Total allowance for loan and lease losses	46,452	45,638	46,099	45,686	45,271	44,858
Loans and leases:
Individually evaluated for impairment	22,123		22,334
Collectively evaluated for impairment	3,632,402		3,510,093
Total loans and leases	3,654,525		3,532,427
Consumer
Allowance for loan and lease losses:
Collectively evaluated for impairment	28,386		28,385
Total allowance for loan and lease losses	28,386	27,923	28,385	26,840	26,632	27,041
Loans and leases:
Collectively evaluated for impairment	1,452,088		1,401,561
Total loans and leases	1,452,088		1,401,561
Unallocated
Allowance for loan and lease losses:
Collectively evaluated for impairment	2,054		3,805
Total allowance for loan and lease losses	$ 2,054	$ 4,741	$ 3,805	$ 10,566	$ 10,395	$ 8,931