Condensed Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 77,669	$ 46,003
Available for sale securities:
Unrealized (losses) gains arising during the period	(42,190)	4,142
Income tax benefit (expense) related to unrealized (losses) gains	10,771	(1,604)
Reclassification adjustment for net realized losses in earnings	0	2
Income tax benefit related to realized losses	0	(1)
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	(31,419)	2,539
Junior subordinated debentures, at fair value
Unrealized losses arising during the period	(1,683)	0
Income tax benefit related to unrealized losses	430	0
Net change in unrealized losses for junior subordinated debentures, at fair value	(1,253)	0
Other comprehensive (loss) income, net of tax	(32,672)	2,539
Comprehensive income	$ 44,997	$ 48,542