CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Comprehensive income (loss):
Net income (loss)	$ 524,668	$ 551,943	$ 250,349
Other comprehensive income:
Unrealized gains (losses) on available-for-sale securities, net	24,218	(88,527)	(263,049)
Reclassification adjustment for net losses included in net income for other-than-temporary credit impairment losses	61,856	57,987	67,444
Reclassification adjustment for net realized losses (gains) included in net income	(7,278)	(25,145)	(77,284)
Other comprehensive income (loss)	78,796	(55,685)	(272,889)
Comprehensive income (loss) before preferred stock dividends	603,464	496,258	(22,540)
Dividends on preferred stock	33,484	2,449	0
Comprehensive income (loss) available to common stock shareholders	$ 569,980	$ 493,809	$ (22,540)