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, 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
Net income		78,070					78,070
Issuance of common stock, net of expenses (in shares)	[1]			589,000
Issuance of common stock, net of expenses	[1]	306		$ 4		302
Repurchase of shares of common stock (in shares)	[1]			(196,000)
Repurchase of shares of common stock	[1]	(1,324)				(1,324)
Equity based compensation expense		1,130				1,130
Accrued dividends attributable to stock-based awards		(173)				(173)
Dividends declared on common stock		(74,215)					(74,215)
Dividends declared on preferred stock		(3,750)					(3,750)
Dividends attributable to dividend equivalents		(218)					(218)
Change in unrealized gains on MBS, net		(56,099)						(56,099)
Derivative hedging instrument fair value changes, net		(49,342)						(49,342)
Balance (in shares) at Mar. 31, 2016			8,000,000	370,977,000
Balance at Mar. 31, 2016		2,861,646	$ 80	$ 3,710		3,019,891	(572,445)	410,410
Increase (Decrease) in Stockholders' Equity
Adjustments related to tax withholding for share-based compensation				$ 1,300
Shares paid for tax withholding for share based compensation (in shares)				196,333
Balance (in shares) at Dec. 31, 2016			8,000,000	371,854,000
Balance at Dec. 31, 2016		3,033,902	$ 80	$ 3,719		3,029,062	(572,641)	573,682
Increase (Decrease) in Stockholders' Equity
Net income		78,060					78,060
Issuance of common stock, net of expenses (in shares)	[1]			1,457,000
Issuance of common stock, net of expenses	[1]	$ 3,956		$ 9		3,947
Repurchase of shares of common stock (in shares)		0		(492,000)	[1]
Repurchase of shares of common stock	[1]	$ (3,859)				(3,859)
Equity based compensation expense		1,024				1,024
Accrued dividends attributable to stock-based awards		429				429
Dividends declared on common stock		(74,569)					(74,569)
Dividends declared on preferred stock		(3,750)					(3,750)
Dividends attributable to dividend equivalents		(227)					(227)
Change in unrealized gains on MBS, net		9,084						9,084
Derivative hedging instrument fair value changes, net		11,897						11,897
Balance (in shares) at Mar. 31, 2017			8,000,000	372,819,000
Balance at Mar. 31, 2017		$ 3,055,947	$ 80	$ 3,728		$ 3,030,603	$ (573,127)	$ 594,663
Increase (Decrease) in Stockholders' Equity
Adjustments related to tax withholding for share-based compensation				$ 3,900
Shares paid for tax withholding for share based compensation (in shares)				492,447

[1] For the three months ended March 31, 2017 and 2016, includes approximately $3.9 million (492,447 shares) and $1.3 million (196,333 shares), respectively surrendered for tax purposes related to equity-based compensation awards.