UNAUDITED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 58,201	$ 38,825
Net unrealized gains (losses) on securities available-for-sale:
Net unrealized gains (losses) arising during the period (net of $(6,783) and $7,030 tax effect, respectively)	22,593	(23,392)
Reclassification adjustments for gains (losses) realized in net income (net of $(3) and $3 tax effect, respectively)	9	(9)
Net unrealized gains (losses) on securities available-for-sale	22,602	(23,401)
Unrealized gains (losses) on derivative instruments designated as cash flow hedges:
Net unrealized gains (losses) arising during the period (net of $(11,112) and $2,645 tax effect, respectively)	37,011	(8,633)
Reclassification adjustments for losses realized in net income (net of $(348) and $(77) tax effect, respectively)	1,160	256
Net change in unrealized gains (losses) on derivative instruments	38,171	(8,377)
Other comprehensive gains (losses), net of tax	60,773	(31,778)
Comprehensive income	$ 118,974	$ 7,047