Consolidated Statements of Comprehensive Income - Unaudited - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 6,029	$ 7,754	$ 53,833	$ 57,222
Unrealized (losses) gains on available-for-sale debt securities:
Unrealized (losses) gains arising during the period	(1,629)	(3,570)	(47,917)	15,192
Income tax effect	423	1,393	12,458	(5,924)
Reclassification adjustments for losses (gains) on securities included in net income	18,659	(5,349)	18,659	(8,532)
Income tax effect	4,851	(2,086)	4,851	(3,327)
Net unrealized gains (losses) on available-for-sale debt securities	12,602	(5,440)	(21,651)	4,063
Unrealized gains on cash flow hedges:
Unrealized gains (losses) arising during the period	4,062	171	6,830	(189)
Income tax effect	(1,056)	(67)	(1,775)	74
Reclassification adjustment for (gains) losses included in net income	(2,519)	572	(2,647)	2,166
Income tax effect	655	(223)	688	(845)
Net unrealized gains on cash flow hedges	1,142	453	3,096	1,206
Other comprehensive income (loss), net of income tax effect	13,744	(4,987)	(18,555)	5,269
Comprehensive income	$ 19,773	$ 2,767	$ 35,278	$ 62,491