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, 2015	$ 2,946,188	$ 1,877	$ 3,366,568	$ 773,791	$ 1,891,239	$ (3,087,287)		$ 0		$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	330,042				330,042
Other comprehensive income (loss)	123,912			123,912
Stock based compensation	1,375		1,375
Common dividends declared	(364,717)					(364,717)
Preferred dividends declared	0
Ending Balance at Sep. 30, 2016	3,036,800	1,877	3,367,943	897,703	2,221,281	(3,452,004)		0		0
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)	417,060				417,060
Other comprehensive income (loss)	95,012			95,012
Stock based compensation	2,755	1	2,754
Common dividends declared	(282,275)					(282,275)
Preferred dividends declared	(24,083)					(24,083)	$ (9,000)		$ (15,000)
Issuance of preferred stock	314,429		314,299							130
Ending Balance at Sep. 30, 2017	$ 3,646,431	$ 1,878	$ 3,825,832	$ 813,118	$ 2,860,244	$ (3,854,829)		$ 58		$ 130