CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Capital in Excess of Par Value	Accumulated Deficit	Accumulated Distributions	Accumulated Other Comprehensive Income (Loss)
Balance (in shares) at Dec. 31, 2013		322,627
Balance at Dec. 31, 2013	$ 1,368,378	$ 3,226	$ 2,846,265	$ (401,985)	$ (1,073,422)	$ (5,706)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Subscriptions received for stock through public offering reinvestment plan (in shares)		3,970
Subscriptions received for stock through public offering reinvestment plan	27,209	$ 40	27,169
Redemption of common stock (in shares)		(1,413)
Redemption of common stock	(9,609)	$ (14)	(9,595)
Net income (loss)	(92,144)			(92,144)
Distributions, declared and paid ($0.4252 per share for 2014, $1.5000 per share for 2015, and $0.6500 per share for 2016)	(137,880)				(137,880)
Foreign currency translation adjustment	(2,933)					(2,933)
Amortization of loss on termination of cash flow hedges	3,486					3,486
Current period adjustment to recognize changes in fair value of cash flow hedges, net of reclassification	883					883
Balance (in shares) at Dec. 31, 2014		325,184
Balance at Dec. 31, 2014	1,157,390	$ 3,252	2,863,839	(494,129)	(1,211,302)	(4,270)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Redemption of common stock (in shares)		(1)
Redemption of common stock	(6)		(6)
Net income (loss)	129,893			129,893
Distributions, declared and paid ($0.4252 per share for 2014, $1.5000 per share for 2015, and $0.6500 per share for 2016)	(487,774)				(487,774)
Foreign currency translation adjustment	(4,970)					(4,970)
Amortization of loss on termination of cash flow hedges	180					180
Current period adjustment to recognize changes in fair value of cash flow hedges, net of reclassification	$ 204					204
Balance (in shares) at Dec. 31, 2015	325,183	325,183
Balance at Dec. 31, 2015	$ 794,917	$ 3,252	2,863,833	(364,236)	(1,699,076)	(8,856)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	65,948			65,948
Distributions, declared and paid ($0.4252 per share for 2014, $1.5000 per share for 2015, and $0.6500 per share for 2016)	(211,369)				(211,369)
Foreign currency translation adjustment	631					631
Amortization of loss on termination of cash flow hedges	0
Current period adjustment to recognize changes in fair value of cash flow hedges, net of reclassification	$ 202					202
Balance (in shares) at Dec. 31, 2016	325,183	325,183
Balance at Dec. 31, 2016	$ 650,329	$ 3,252	$ 2,863,833	$ (298,288)	$ (1,910,445)	$ (8,023)