Stockholders' Equity - Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	$ 1,903,211	$ 1,928,255	$ 1,855,473
Total other comprehensive (loss) income	41,854	(11,205)	(3,527)
Balance at end of period	2,036,011	1,903,211	1,928,255
AOCI Attributable to Parent
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	(32,705)	(21,781)	(14,657)
Unrealized gains (losses) on securities available for sale	59,851	(16,201)	(5,796)
Reclassification adjustments for net gains realized in income	(282)	0	(301)
Tax effect	(17,715)	4,996	2,570
Total other comprehensive (loss) income	41,854	(11,205)	(3,527)
Reclassification to retained earnings due to the tax reform	0	0	(3,597)
Reclassification to retained earnings per ASU 2016-01	0	281	0
Balance at end of period	$ 9,149	(32,705)	(21,781)
Amount reclassified out of accumulated other comprehensive loss to reflect gain on sale of securities		0	301
AOCI Attributable to Parent | Accounting Standards Update 2016-01
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Reclassification to retained earnings per ASU 2016-01		$ 281
AOCI Attributable to Parent | Accounting Standards Update 2018-02
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Reclassification to retained earnings due to the tax reform			$ (3,600)