CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY (UNAUDITED) - 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		160,244					160,244
Issuance of common stock, net of expenses	[1]	623		$ 1		622
Issuance of common stock, net of expenses (in shares)	[1]			134,000
Repurchase of shares of common stock	[1]	(238)				(238)
Repurchase of shares of common stock (in shares)	[1]			(22,000)
Equity based compensation expense		2,569				2,569
Accrued dividends attributable to stock-based awards		(225)				(225)
Dividends declared on common stock		(148,153)					(148,153)
Dividends declared on preferred stock		(7,500)					(7,500)
Dividends attributable to dividend equivalents		(513)					(513)
Change in unrealized losses on MBS, net		(58,901)						(58,901)
Change in unrealized losses on derivative hedging instruments, net		(5,509)						(5,509)
Balance (in shares) at Jun. 30, 2015			8,000,000	370,196,000
Balance at Jun. 30, 2015		3,145,669	$ 80	$ 3,702		3,016,362	(569,055)	694,580
Increase (Decrease) in Stockholders' Equity
Adjustments Related to Tax Withholding for Share-based Compensation				$ 169
Shares Paid for Tax Withholding for Share Based Compensation (in shares)				22,148
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		157,020					157,020
Issuance of common stock, net of expenses	[1]	600		$ 4		596
Issuance of common stock, net of expenses (in shares)	[1]			647,000
Repurchase of shares of common stock	[1]	$ (1,384)				(1,384)
Repurchase of shares of common stock (in shares)		0		(204,000)	[1]
Equity based compensation expense		$ 3,038				3,038
Accrued dividends attributable to stock-based awards		(345)				(345)
Dividends declared on common stock		(148,438)					(148,438)
Dividends declared on preferred stock		(7,500)					(7,500)
Dividends attributable to dividend equivalents		(459)					(459)
Change in unrealized losses on MBS, net		40,447						40,447
Change in unrealized losses on derivative hedging instruments, net		(62,572)						(62,572)
Balance (in shares) at Jun. 30, 2016			8,000,000	371,027,000
Balance at Jun. 30, 2016		$ 2,947,668	$ 80	$ 3,710		$ 3,021,861	$ (571,709)	$ 493,726
Increase (Decrease) in Stockholders' Equity
Adjustments Related to Tax Withholding for Share-based Compensation				$ 1,400
Shares Paid for Tax Withholding for Share Based Compensation (in shares)				204,451

[1] For the six months ended June 30, 2016 and 2015, includes approximately $1.4 million (204,451 shares) and $169,000 (22,148 shares), respectively surrendered for tax purposes related to equity-based compensation awards.