CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS’ EQUITY - USD ($) $ in Thousands	Total	Common Stock	Capital in Excess of Par Value	Accumulated Distributions in Excess of Earnings	Accumulated Other Comprehensive (Loss) Income	Cumulative effect of accounting changes	Cumulative effect of accounting changes Common Stock	Cumulative effect of accounting changes Capital in Excess of Par Value	Cumulative effect of accounting changes Accumulated Distributions in Excess of Earnings
Balance, (shares) at Dec. 31, 2018		311,381,396
Balance at Dec. 31, 2018	$ 1,816,850	$ 3,114	$ 2,607,330	$ (804,617)	$ 11,023
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock (shares)		2,267,609
Issuance of common stock	21,247	$ 22	21,225
Equity-based compensation	32		32
Distributions declared on common stock	(47,963)			(47,963)
Redemptions of common stock (shares)		(2,318,505)
Redemptions of common stock	(21,724)	$ (23)	(21,701)
Changes in redeemable common stock	(67)		(67)
Comprehensive income (loss)	3,496			8,817	(5,321)
Balance, (shares) at Mar. 31, 2019		311,330,500
Balance at Mar. 31, 2019	1,771,871	$ 3,113	2,606,819	(843,763)	5,702
Balance, (shares) at Dec. 31, 2018		311,381,396
Balance at Dec. 31, 2018	1,816,850	$ 3,114	2,607,330	(804,617)	11,023
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income (loss)	4,396
Balance, (shares) at Sep. 30, 2019		311,268,549
Balance at Sep. 30, 2019	1,675,343	$ 3,113	2,606,885	(929,743)	(4,912)
Balance, (shares) at Mar. 31, 2019		311,330,500
Balance at Mar. 31, 2019	1,771,871	$ 3,113	2,606,819	(843,763)	5,702
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock (shares)		2,436,153
Issuance of common stock	21,073	$ 25	21,048
Equity-based compensation	32		32
Distributions declared on common stock	(48,487)			(48,487)
Redemptions of common stock (shares)		(2,440,984)
Redemptions of common stock	(21,115)	$ (25)	(21,090)
Changes in redeemable common stock	42		42
Comprehensive income (loss)	(258)			8,973	(9,231)
Balance, (shares) at Jun. 30, 2019		311,325,669					2,361,229
Balance at Jun. 30, 2019	1,723,158	$ 3,113	2,606,851	(883,277)	(3,529)	$ 20,425	$ 24	$ 20,401
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock	34		34
Distributions declared on common stock	(49,007)			(49,007)
Redemptions of common stock (shares)		(2,418,349)
Redemptions of common stock	(20,919)	$ (24)	(20,895)
Changes in redeemable common stock	494		494
Comprehensive income (loss)	1,158			2,541	(1,383)
Balance, (shares) at Sep. 30, 2019		311,268,549
Balance at Sep. 30, 2019	$ 1,675,343	$ 3,113	2,606,885	(929,743)	(4,912)
Balance, (shares) at Dec. 31, 2019	311,207,725	311,207,725
Balance at Dec. 31, 2019	$ 1,789,948	$ 3,112	2,606,925	(816,181)	(3,908)	(2,002)			$ (2,002)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock (shares)		2,223,298
Issuance of common stock	19,231	$ 22	19,209
Equity-based compensation	40		40
Distributions declared on common stock	(48,332)			(48,332)
Redemptions of common stock (shares)		(2,256,037)
Redemptions of common stock	(19,514)	$ (22)	(19,492)
Changes in redeemable common stock	283		283
Comprehensive income (loss)	(22,003)			(12,175)	(9,828)
Balance, (shares) at Mar. 31, 2020		311,174,986
Balance at Mar. 31, 2020	$ 1,717,651	$ 3,112	2,606,965	(878,690)	(13,736)
Balance, (shares) at Dec. 31, 2019	311,207,725	311,207,725
Balance at Dec. 31, 2019	$ 1,789,948	$ 3,112	2,606,925	(816,181)	(3,908)	$ (2,002)			$ (2,002)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income (loss)	$ (15,027)
Balance, (shares) at Sep. 30, 2020	309,405,505	309,405,505
Balance at Sep. 30, 2020	$ 1,850,418	$ 3,094	2,774,027	(919,510)	(7,193)
Balance, (shares) at Mar. 31, 2020		311,174,986
Balance at Mar. 31, 2020	1,717,651	$ 3,112	2,606,965	(878,690)	(13,736)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock (shares)		1,242,475
Issuance of common stock	9,543	$ 12	9,531
Equity-based compensation	40		40
Distributions declared on common stock	(13,072)			(13,072)
Redemptions of common stock (shares)		(2,468,754)
Redemptions of common stock	(19,191)	$ (25)	(19,166)
Changes in redeemable common stock	9,643		9,643
Comprehensive income (loss)	(1,188)			(3,746)	2,558
Balance, (shares) at Jun. 30, 2020		309,948,707
Balance at Jun. 30, 2020	1,703,426	$ 3,099	2,607,013	(895,508)	(11,178)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock (shares)		746,001
Issuance of common stock	5,417	$ 8	5,409
Equity-based compensation	40		40
Distributions declared on common stock	(28,181)			(28,181)
Redemptions of common stock (shares)		(1,289,203)
Redemptions of common stock	(9,360)	$ (13)	(9,347)
Changes in redeemable common stock	170,912		170,912
Comprehensive income (loss)	$ 8,164			4,179	3,985
Balance, (shares) at Sep. 30, 2020	309,405,505	309,405,505
Balance at Sep. 30, 2020	$ 1,850,418	$ 3,094	$ 2,774,027	$ (919,510)	$ (7,193)