Condensed Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 84,502	$ 90,981	$ 270,345	$ 235,952
Available for sale securities:
Unrealized gains (losses) arising during the period	26,352	(29,262)	100,381	(75,479)
Income tax (expense) benefit related to unrealized gains (losses)	(6,778)	7,471	(25,819)	19,270
Reclassification adjustment for net realized losses (gains) in earnings	0	0	7,186	(14)
Income tax (benefit) expense related to realized losses (gains)	0	0	(1,848)	4
Net change in unrealized gains (losses) for available for sale securities	19,574	(21,791)	79,900	(56,219)
Junior subordinated debentures, at fair value:
Unrealized gains (losses) arising during the period	8,450	(2,409)	32,254	(5,605)
Income tax (expense) benefit related to unrealized gains (losses)	(2,173)	615	(8,276)	1,431
Net change in unrealized gains (losses) for junior subordinated debentures, at fair value	6,277	(1,794)	23,978	(4,174)
Other comprehensive income (loss), net of tax	25,851	(23,585)	103,878	(60,393)
Comprehensive income	$ 110,353	$ 67,396	$ 374,223	$ 175,559