CONSOLIDATED STATEMENT OF CHANGES IN STOCKHOLDERS' EQUITY (UNAUDITED) - USD ($) $ in Thousands		Total	Preferred Stock Series B 7.50% Cumulative Redeemable - Liquidation Preference $25.00 per Share	Common Stock		Additional Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive Income
Balance at Dec. 31, 2013		$ 3,142,251	$ 80	$ 3,651		$ 2,972,369	$ (571,544)	$ 737,695
Balance (in shares) at Dec. 31, 2013			8,000,000	365,125,000
Increase (Decrease) in Stockholders' Equity
Cumulative effect adjustment on adoption of revised accounting standard for repurchase agreement financing		0
Net income		233,796					233,796	0
Issuance of common stock, net of expenses	[1]	26,371		$ 36		26,335	0	0
Issuance of common stock, net of expenses (in shares)	[1]			3,690,000
Repurchase of shares of common stock	[1]	(348)		$ 0		(348)	0	0
Repurchase of shares of common stock (in shares)	[1]			(94,000)
Equity based compensation expense		4,357				4,357	0	0
Accrued dividends attributable to stock-based awards		(164)				(164)	0	0
Dividends declared on common stock		(220,724)				0	(220,724)	0
Dividends declared on preferred stock		(11,250)				0	(11,250)	0
Dividends attributable to dividend equivalents		(384)				0	(384)	0
Change in unrealized gains on MBS, net		95,793				0	0	95,793
Change in unrealized losses on derivative hedging instruments, net		(15,954)				0	0	(15,954)
Balance at Sep. 30, 2014		3,253,744	$ 80	$ 3,687		3,002,549	(570,106)	817,534
Balance (in shares) at Sep. 30, 2014			8,000,000	368,721,000
Balance at Dec. 31, 2014		3,203,272	$ 80	$ 3,701		3,013,634	(568,596)	754,453
Balance (in shares) at Dec. 31, 2014			8,000,000	370,084,000
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	0
Issuance of common stock, net of expenses	[1]	926		$ 1		925	0	0
Issuance of common stock, net of expenses (in shares)	[1]			212,000
Repurchase of shares of common stock	[1]	$ (466)		$ 0		(466)	0	0
Repurchase of shares of common stock (in shares)		0		(42,000)	[1]
Equity based compensation expense		$ 3,600				3,600	0	0
Accrued dividends attributable to stock-based awards		(338)				(338)	0	0
Dividends declared on common stock		(222,242)				0	(222,242)	0
Dividends declared on preferred stock		(11,250)				0	(11,250)	0
Dividends attributable to dividend equivalents		(778)				0	(778)	0
Change in unrealized gains on MBS, net		(114,303)				0	0	(114,303)
Change in unrealized losses on derivative hedging instruments, net		(46,393)				0	0	(46,393)
Balance at Sep. 30, 2015		$ 3,051,782	$ 80	$ 3,702		$ 3,017,355	$ (567,649)	$ 598,294
Balance (in shares) at Sep. 30, 2015			8,000,000	370,254,000

[1] For the nine months ended September 30, 2015 and 2014, includes approximately $465,000 (42,357 shares) and $721,000 (94,073 shares), respectively, surrendered for tax purposes related to equity-based compensation awards.