Allowance for Credit Losses - Activity in Allowance for Loan Losses (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance	$ 132,862	$ 115,443	$ 120,856	$ 114,419
Loans charged-off	(2,201)	(4,289)	(3,921)	(7,668)
Charged-off loans recovered	1,509	1,582	4,533	3,583
Net recoveries (charge-offs)	(692)	(2,707)	612	(4,085)
Provision for loan losses	6,592	3,710	17,294	6,112
Ending balance	138,762	116,446	138,762	116,446
Commercial and Industrial
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance	66,546	51,288	57,232	50,820
Loans charged-off	(642)	(2,910)	(773)	(4,624)
Charged-off loans recovered	819	312	2,926	1,160
Net recoveries (charge-offs)	177	(2,598)	2,153	(3,464)
Provision for loan losses	7,534	2,927	14,872	4,261
Ending balance	74,257	51,617	74,257	51,617
Commercial Real Estate
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance	56,679	56,302	54,954	55,851
Loans charged-off	(38)	(139)	(348)	(553)
Charged-off loans recovered	15	640	384	782
Net recoveries (charge-offs)	(23)	501	36	229
Provision for loan losses	(2,844)	(1,348)	(1,178)	(625)
Ending balance	53,812	55,455	53,812	55,455
Residential Mortgage
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance	4,100	3,592	3,605	3,702
Loans charged-off	(99)	(229)	(167)	(359)
Charged-off loans recovered	180	235	260	683
Net recoveries (charge-offs)	81	6	93	324
Provision for loan losses	443	588	926	160
Ending balance	4,624	4,186	4,624	4,186
Consumer
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance	5,537	4,261	5,065	4,046
Loans charged-off	(1,422)	(1,011)	(2,633)	(2,132)
Charged-off loans recovered	495	395	963	958
Net recoveries (charge-offs)	(927)	(616)	(1,670)	(1,174)
Provision for loan losses	1,459	1,543	2,674	2,316
Ending balance	$ 6,069	$ 5,188	$ 6,069	$ 5,188