Condensed Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 74,033	$ 78,972
Available for sale securities:
Unrealized gains (losses) arising during the period	33,269	(42,190)
Income tax (expense) benefit related to unrealized gains (losses)	(8,557)	10,771
Net change in unrealized gains (losses) for available for sale securities	24,712	(31,419)
Junior subordinated debentures, at fair value:
Unrealized gains (losses) arising during the period	6,564	(1,683)
Income tax (expense) benefit related to unrealized gains (losses)	(1,644)	430
Net change in unrealized gains (losses) for junior subordinated debentures, at fair value	4,920	(1,253)
Other comprehensive income (loss), net of tax	29,632	(32,672)
Comprehensive income	$ 103,665	$ 46,300