Related Party Arrangements - Issuance of Common Stock to the Advisor (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Dec. 31, 2019
Related Party Transaction [Line Items]
Share-based payment of advisor asset management fees (in shares)							1,200,000
Share-based payment of advisor asset management fees	$ 2,500	$ 2,500	$ 2,500	$ 2,500	$ 2,500	$ 2,500
Common stock (in shares)	190,020,662						190,020,662	189,111,561
Common stock	$ 1,900						$ 1,900	$ 1,891
The Advisor, the Sponsor, and affiliates
Related Party Transaction [Line Items]
Common stock (in shares)	4,300,000						4,300,000
Common stock	$ 26,900						$ 26,900
Common stock, outstanding (percentage)	1.90%						1.90%