Equity (Narrative) (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended			6 Months Ended	9 Months Ended		40 Months Ended
	Jan. 25, 2020	Sep. 30, 2021	Sep. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Dec. 31, 2021	Dec. 31, 2020	Jun. 13, 2018
Subsidiary, Sale of Stock [Line Items]
Preferred Stock, Shares Issued		4,600,000				4,600,000		4,600,000		4,600,000
Preferred Stock, Dividend Rate, Percentage					6.75%	6.75%
Preferred Stock, Shares Outstanding		4,600,000				4,600,000		4,600,000		4,600,000
Preferred Stock, Shares Authorized		100,000,000				100,000,000		100,000,000		100,000,000
Preferred Stock, Par or Stated Value Per Share		$ 0.001				$ 0.001		$ 0.001		$ 0.001
Preferred Stock, Liquidation Preference Per Share		$ 25.00				$ 25.00		$ 25.00
Preferred Stock, Amount of Preferred Dividends in Arrears					$ 1,300	$ 1,300
Preferred Stock Dividend Rate Variable Rate Spread						5.196%
Common stock, shares authorized (in shares)		100,000,000				100,000,000		100,000,000		100,000,000
Common Stock, Par or Stated Value Per Share		$ 0.001				$ 0.001		$ 0.001		$ 0.001
Dividends declared (in usd per share)		$ 0.45	$ 0.27			$ 1.19	$ 0.97
Dividends paid						$ (58,469)	$ (50,642)
Common shares issued and outstanding upon conversion of all convertible securities (in shares)		52,366,399				52,366,399		52,366,399	44,442,631
Number of shares authorized to be repurchased (in shares)											1,550,000
Shares repurchased (in shares)		0	1,878			0	290,050	701,965
Average price per share (USD per share)			$ 11.00				$ 10.54	$ 13.36
Total cost			$ (21)	$ (3,035)			$ (3,100)	$ (9,400)
Stock Issued During Period, Shares, New Issues	5,290,000	7,852,900	0			7,852,900	5,290,000
Proceeds from issuance of shares, net	$ 95,300
Shares Issued As Payment of Incentive Fee, Shares		37,373	0			37,373	637
Maximum shares available to be issued under at the market program						10,000,000
Over-Allotment Option [Member]
Subsidiary, Sale of Stock [Line Items]
Stock Issued During Period, Shares, New Issues	690,000
At-the-market program
Subsidiary, Sale of Stock [Line Items]
Stock Issued During Period, Shares, New Issues		1,549,900				1,549,900
Proceeds from issuance of shares, net		$ 28,200				$ 28,200
Agent commissions		$ 400				$ 400
Operating Partnership Units [Member]
Subsidiary, Sale of Stock [Line Items]
Stock issued during period, shares, conversion of units		5,710	3,638			5,710	133,154