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, 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)	277,824				277,824
Other comprehensive income (loss)	62,177			62,177
Stock based compensation	1,603	1	1,602
Common dividends declared	(188,196)					(188,196)
Preferred dividends declared	(14,683)					(14,683)	$ (6,000)		$ (9,000)
Issuance of preferred stock	314,429		314,299							130
Ending Balance at Jun. 30, 2017	3,576,687	1,878	3,824,680	780,283	2,721,008	(3,751,350)		58		130
Beginning Balance at Dec. 31, 2017	3,634,977	1,878	3,826,691	796,902	2,967,852	(3,958,534)		58		130
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	357,116				357,116
Other comprehensive income (loss)	(125,251)			(125,251)
Repurchase of common stock	(14,834)	(8)	(14,826)
Stock based compensation	4,766		4,766
Common dividends declared	(187,832)					(187,832)
Preferred dividends declared	(18,800)					(18,800)	$ (6,000)		$ (13,000)
Ending Balance at Jun. 30, 2018	$ 3,650,142	$ 1,870	$ 3,816,631	$ 671,651	$ 3,324,968	$ (4,165,166)		$ 58		$ 130