CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in Thousands		Total	Common Stock Par Value	Additional Paid-in Capital	Accumulated Other Comprehensive Income	Cumulative Earnings	Cumulative Distributions to Stockholders	Series A Preferred Stock Par Value	Series A Preferred Stock Par Value Preferred Stock	Series B Preferred Stock Par Value	Series B Preferred Stock Par Value Preferred Stock
Beginning Balance at Dec. 31, 2014		$ 3,607,690	$ 2,055	$ 3,614,409	$ 1,046,680	$ 1,653,029	$ (2,708,483)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)		250,349				250,349
Cumulative effect of accounting change	[1]	(12,137)				(12,137)
Other comprehensive income (loss)		(272,889)			(272,889)
Stock based compensation		1,979	2	1,977
Repurchase of common stock		(250,000)	(180)	(249,820)
Common dividends declared		(378,804)					(378,804)
Preferred dividends declared		0
Ending Balance at Dec. 31, 2015		2,946,188	1,877	3,366,566	773,791	1,891,241	(3,087,287)		$ 0		$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)		551,943				551,943
Other comprehensive income (loss)		(55,685)			(55,685)
Stock based compensation		2,206		2,206
Common dividends declared		(458,735)					(458,735)
Preferred dividends declared		(2,449)					(2,449)
Issuance of preferred stock		140,065		140,007					58
Ending Balance at Dec. 31, 2016		3,123,533	1,877	3,508,779	718,106	2,443,184	(3,548,471)		58		0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)		524,668				524,668
Other comprehensive income (loss)		78,796			78,796
Stock based compensation		3,614	1	3,613
Common dividends declared		(376,579)					(376,579)
Preferred dividends declared		(33,484)					(33,484)	$ (12,000)		$ (22,000)
Issuance of preferred stock		314,429		314,299							130
Ending Balance at Dec. 31, 2017		$ 3,634,977	$ 1,878	$ 3,826,691	$ 796,902	$ 2,967,852	$ (3,958,534)		$ 58		$ 130

[1] Adoption of ASU No. 2014-13, Measuring the Financial Assets and the Financial Liabilities of a Consolidated Collateralized Financing Entity.