Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement of Comprehensive Income [Abstract]
Net Income (Loss) Attributable to Parent	$ (1,523,420)	$ 354,095	$ 316,263
Available for sale securities:
Unrealized gains (losses) arising during the period	106,814	86,029	(35,205)
Income tax (expense) benefit related to unrealized gains (losses)	(27,473)	(22,127)	8,911
Reclassification adjustment for net realized (gains) losses in earnings	(190)	7,184	(14)
Income tax expense (benefit) related to realized (gains) losses	49	(1,848)	4
Net change in unrealized gains (losses) for available for sale securities	79,200	69,238	(26,304)
Junior subordinated debentures, at fair value:
Unrealized gains (losses) arising during the period	18,842	25,855	(23,268)
Income tax (expense) benefit related to unrealized gains (losses)	(4,846)	(6,630)	5,940
Net change in unrealized gains (losses) for junior subordinated debentures, at fair value	13,996	19,225	(17,328)
Other comprehensive income (loss), net of tax	93,196	88,463	(43,632)
Comprehensive (loss) income	$ (1,430,224)	$ 442,558	$ 272,631