Consolidated Statements of Equity (Unaudited) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Cumulative Distributions	Accumulated Deficit	Accumulated Other Comprehensive Income	Total Stockholders’ Equity	Non- controlling Interests
Beginning balance (shares) at Dec. 31, 2017		77,175,283
Beginning balance at Dec. 31, 2017	$ 562,544	$ 76	$ 656,705	$ (82,590)	$ (12,672)	$ 949	$ 562,468	$ 76
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Gross proceeds from issuance of common stock (shares)		762,537
Gross proceeds from issuance of common stock	7,430	$ 1	7,429				7,430
Changes in redeemable common stock	(6,538)		(6,538)				(6,538)
Discount on issuance of common stock	(1)		(1)				(1)
Stock-based compensation (in shares)		10,500
Stock-based compensation	44		44				44
Offering costs including dealer manager fees and stockholder servicing fees to affiliates	(1,140)		(1,140)				(1,140)
Distributions to common stockholders	(22,709)			(22,709)			(22,709)
Issuance of shares for distribution reinvestment plan (shares)		2,083,950
Issuance of shares for distribution reinvestment plan	0	$ 2	19,996	(19,998)
Repurchase of common stock (in shares)		(2,506,299)
Repurchase of common stock	(23,766)	$ (3)	(23,763)	0			(23,766)
Additions to common stock subject to redemption	3,768	$ 0	3,768				3,768
Issuance of stock dividends (in shares)		2
Issuance of limited partnership units	1,185							1,185
Distributions to noncontrolling interest	(70)							(70)
Net (loss)	(3,287)				(3,281)		(3,281)	(6)
Other comprehensive loss	$ (952)					(949)	(949)	(3)
Ending balance (shares) at Dec. 31, 2018	77,525,973	77,525,973
Ending balance at Dec. 31, 2018	$ 516,508	$ 76	656,500	(125,297)	(15,953)	0	515,326	1,182
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation (in shares)		10,500
Stock-based compensation	106		106				106
Offering costs including dealer manager fees and stockholder servicing fees to affiliates	(13)		(13)				(13)
Distributions to common stockholders	(7,193)			(7,193)			(7,193)
Issuance of shares for distribution reinvestment plan (shares)		345,400
Issuance of shares for distribution reinvestment plan	3,323	$ 1	3,322	(3,323)
Additions to common stock subject to redemption	83		83				83
Issuance of limited partnership units	3,904							3,904
Distributions to noncontrolling interest	(47)							(47)
Net (loss)	$ (1,647)				(1,640)		(1,640)	(7)
Other comprehensive loss								0
Ending balance (shares) at Mar. 31, 2019	77,881,873	77,881,873
Ending balance at Mar. 31, 2019	$ 511,701	$ 77	$ 659,998	$ (135,813)	$ (17,593)	$ 0	$ 506,669	$ 5,032