CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 166,261	$ 102,353	$ 65,774
Net unrealized (losses) gains on securities available-for-sale:
Net unrealized (losses) gains arising during the period	(23,544)	21,513	(25,361)
Reclassification adjustments for gains (losses) realized in net income	1,425	92	(2,359)
Net unrealized (losses) gains on securities available-for-sale	(22,119)	21,605	(27,720)
Unrealized losses on derivative instruments designated as cash flow hedges:
Net unrealized (losses) arising during the period	(5,934)	(643)	(4,732)
Reclassification adjustments for gains (losses) realized in net income	3,971	(2,339)	(7,106)
Net change in unrealized (losses) on derivative instruments	(1,963)	(2,982)	(11,838)
Change in pension liability:
Actuarial gains (losses) arising during the period	203	37	(145)
Reclassification adjustments for gains realized in net income		84	132
Net unrealized gains (losses) on pension liability	203	121	(13)
Other comprehensive (losses) gains, net of tax	(23,879)	18,744	(39,571)
Comprehensive income	$ 142,382	$ 121,097	$ 26,203