CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in Thousands		Total	Preferred Stock Preferred Stock 7.50% Series B Cumulative Redeemable - Liquidation Preference $25.00 per Share	Common Stock		Additional Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive Income
Balance (in shares) at Dec. 31, 2014			8,000,000	370,084,000
Balance at Dec. 31, 2014		$ 3,203,272	$ 80	$ 3,701		$ 3,013,634	$ (568,596)	$ 754,453
Increase (Decrease) in Stockholders' Equity
Cumulative effect adjustment on adoption of revised accounting standard for repurchase agreement financing		4,537					(4,537)	4,537
Net income		239,754					239,754
Issuance of common stock, net of expenses	[1]	926		$ 1		925
Issuance of common stock, net of expenses (in shares)	[1]			212,000
Repurchase of shares of common stock	[1]	(466)				(466)
Repurchase of shares of common stock (in shares)	[1]			(42,000)
Equity based compensation expense		3,600				3,600
Accrued dividends attributable to stock-based awards		(338)				(338)
Dividends declared on common stock		(222,242)					(222,242)
Dividends declared on preferred stock		(11,250)					(11,250)
Dividends attributable to dividend equivalents		(778)					(778)
Change in unrealized losses on MBS, net		(114,303)						(114,303)
Change in unrealized losses on derivative hedging instruments, net		(46,393)						(46,393)
Balance (in shares) at Sep. 30, 2015			8,000,000	370,254,000
Balance at Sep. 30, 2015		3,051,782	$ 80	$ 3,702		3,017,355	(567,649)	598,294
Increase (Decrease) in Stockholders' Equity
Adjustments related to tax withholding for share-based compensation				$ 465
Shares paid for tax withholding for share based compensation (in shares)				42,357
Balance (in shares) at Dec. 31, 2015			8,000,000	370,584,000
Balance at Dec. 31, 2015		2,967,261	$ 80	$ 3,706		3,019,956	(572,332)	515,851
Increase (Decrease) in Stockholders' Equity
Cumulative effect adjustment on adoption of revised accounting standard for repurchase agreement financing		0
Net income		240,031					240,031
Issuance of common stock, net of expenses	[1]	941		$ 5		936
Issuance of common stock, net of expenses (in shares)	[1]			716,000
Repurchase of shares of common stock	[1]	$ (1,481)				(1,481)
Repurchase of shares of common stock (in shares)		0		(217,000)	[1]
Equity based compensation expense		$ 4,140				4,140
Accrued dividends attributable to stock-based awards		(518)				(518)
Dividends declared on common stock		(222,669)					(222,669)
Dividends declared on preferred stock		(11,250)					(11,250)
Dividends attributable to dividend equivalents		(697)					(697)
Change in unrealized losses on MBS, net		97,483						97,483
Change in unrealized losses on derivative hedging instruments, net		(39,803)						(39,803)
Balance (in shares) at Sep. 30, 2016			8,000,000	371,083,000
Balance at Sep. 30, 2016		$ 3,033,438	$ 80	$ 3,711		$ 3,023,033	$ (566,917)	$ 573,531
Increase (Decrease) in Stockholders' Equity
Adjustments related to tax withholding for share-based compensation				$ 1,500
Shares paid for tax withholding for share based compensation (in shares)				217,464

[1] For the nine months ended September 30, 2016 and 2015, includes approximately $1.5 million (217,464 shares) and $465,000 (42,357 shares), respectively surrendered for tax purposes related to equity-based compensation awards.