Allowance for Credit Losses - Activity in Allowance for Loan Losses (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance	$ 154,381	$ 132,862	$ 151,859	$ 120,856
Loans charged-off	(4,825)	(2,201)	(11,150)	(3,921)
Charged-off loans recovered	1,843	1,509	2,834	4,533
Net (charge-offs) recoveries	(2,982)	(692)	(8,316)	612
Provision for loan losses	3,706	6,592	11,562	17,294
Ending balance	155,105	138,762	155,105	138,762
Commercial and Industrial
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance	94,630	66,546	90,956	57,232
Loans charged-off	(3,073)	(642)	(7,355)	(773)
Charged-off loans recovered	1,195	819	1,678	2,926
Net (charge-offs) recoveries	(1,878)	177	(5,677)	2,153
Provision for loan losses	1,632	7,534	9,105	14,872
Ending balance	94,384	74,257	94,384	74,257
Commercial Real Estate
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance	47,762	56,679	49,650	54,954
Loans charged-off	0	(38)	0	(348)
Charged-off loans recovered	22	15	43	384
Net (charge-offs) recoveries	22	(23)	43	36
Provision for loan losses	1,194	(2,844)	(715)	(1,178)
Ending balance	48,978	53,812	48,978	53,812
Residential Mortgage
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance	5,139	4,100	5,041	3,605
Loans charged-off	0	(99)	(15)	(167)
Charged-off loans recovered	9	180	10	260
Net (charge-offs) recoveries	9	81	(5)	93
Provision for loan losses	71	443	183	926
Ending balance	5,219	4,624	5,219	4,624
Consumer
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance	6,850	5,537	6,212	5,065
Loans charged-off	(1,752)	(1,422)	(3,780)	(2,633)
Charged-off loans recovered	617	495	1,103	963
Net (charge-offs) recoveries	(1,135)	(927)	(2,677)	(1,670)
Provision for loan losses	809	1,459	2,989	2,674
Ending balance	$ 6,524	$ 6,069	$ 6,524	$ 6,069