Allowance for Credit Losses - Activity in Allowance for Loan Losses (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance	$ 151,859	$ 120,856
Loans charged-off	(6,325)	(1,720)
Charged-off loans recovered	991	3,024
Net (charge-offs) recoveries	(5,334)	1,304
Provision for loan losses	7,856	10,702
Ending balance	154,381	132,862
Commercial and Industrial
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance	90,956	57,232
Loans charged-off	(4,282)	(131)
Charged-off loans recovered	483	2,107
Net (charge-offs) recoveries	(3,799)	1,976
Provision for loan losses	7,473	7,338
Ending balance	94,630	66,546
Commercial Real Estate
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance	49,650	54,954
Loans charged-off	0	(310)
Charged-off loans recovered	21	369
Net (charge-offs) recoveries	21	59
Provision for loan losses	(1,909)	1,666
Ending balance	47,762	56,679
Residential Mortgage
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance	5,041	3,605
Loans charged-off	(2,028)	(68)
Charged-off loans recovered	1	80
Net (charge-offs) recoveries	(2,027)	12
Provision for loan losses	2,125	483
Ending balance	5,139	4,100
Consumer
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance	6,212	5,065
Loans charged-off	(15)	(1,211)
Charged-off loans recovered	486	468
Net (charge-offs) recoveries	471	(743)
Provision for loan losses	167	1,215
Ending balance	$ 6,850	$ 5,537