Equity (Narrative) (Details) - USD ($) $ / shares in Units, $ in Thousands							3 Months Ended		9 Months Ended	12 Months Ended			13 Months Ended	40 Months Ended
	Nov. 13, 2021	Oct. 15, 2021	Jul. 31, 2021	Jul. 29, 2021	Jul. 09, 2021	Jan. 25, 2020	Dec. 31, 2021	Jun. 30, 2020	Sep. 30, 2021	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Jul. 29, 2022	Sep. 30, 2021	Jun. 13, 2018
Subsidiary, Sale of Stock [Line Items]
Preferred Stock, Shares Issued							9,400,000			9,400,000	4,600,000
Proceeds from Issuance of Preferred Stock and Preference Stock										$ 116,220	$ 0	$ 111,378
Preferred Stock, Shares Outstanding							9,400,000			9,400,000	4,600,000
Preferred Stock, Shares Authorized							100,000,000			100,000,000	100,000,000
Preferred Stock, Par or Stated Value Per Share							$ 0.001			$ 0.001	$ 0.001
Preferred Stock, Amount of Preferred Dividends in Arrears									$ 1,300
Common stock, shares authorized (in shares)							100,000,000			100,000,000	100,000,000
Common Stock, Par or Stated Value Per Share							$ 0.001			$ 0.001	$ 0.001
Dividends declared (in usd per share)										$ 1.64	$ 1.26	$ 1.81
Dividends paid										$ (85,704)	$ (65,026)	$ (54,312)
Common shares issued and outstanding upon conversion of all convertible securities (in shares)							58,180,342			58,180,342	44,442,631
Number of shares authorized to be repurchased (in shares)															1,550,000
Shares repurchased (in shares)										0	290,050	50,825		701,965
Average price per share (USD per share)											$ 10.54	$ 15.39		$ 13.36
Total cost								$ (3,056)			$ (3,100)	$ (782)		$ (9,400)
Stock Issued During Period, Shares, New Issues		5,750,000			6,000,000	5,290,000				13,602,900	5,290,000	8,855,000	6,303,000
Proceeds from issuance of shares, net						$ 95,300
Stock issued during period, shares, conversion of units										0	0	13,092
Shares Issued As Payment of Incentive Fee, Shares	30,502		37,373							67,875	637	0
Stock Issued During Period, Value, New Issues		$ 103,500											$ 113,100
Series A Preferred Stock
Subsidiary, Sale of Stock [Line Items]
Preferred Stock, Dividend Rate, Percentage										6.75%
Preferred Stock, Shares Outstanding							4,600,000			4,600,000
Preferred Stock, Par or Stated Value Per Share							$ 0.001			$ 0.001
Preferred Stock, Liquidation Preference Per Share							$ 25.00			$ 25.00
Preferred Stock, Amount of Preferred Dividends in Arrears										$ 1,600	$ 1,300
Preferred Stock Dividend Rate Variable Rate Spread										5.196%
Series B Preferred Stock
Subsidiary, Sale of Stock [Line Items]
Preferred Stock, Dividend Rate, Percentage										6.25%
Preferred Stock, Shares Outstanding							4,800,000			4,800,000
Preferred Stock, Par or Stated Value Per Share							$ 0.001			$ 0.001
Preferred Stock, Liquidation Preference Per Share							$ 25.00			$ 25.00
Preferred Stock Dividend Rate Variable Rate Spread										4.99%
Over-Allotment Option [Member]
Subsidiary, Sale of Stock [Line Items]
Stock Issued During Period, Shares, New Issues		750,000		303,000		690,000
At-the-market program
Subsidiary, Sale of Stock [Line Items]
Stock Issued During Period, Shares, New Issues							1,549,900
Proceeds from issuance of shares, net							$ 28,200
Agent commissions							$ 400
Common ATM Program
Subsidiary, Sale of Stock [Line Items]
Stock Issued During Period, Shares, New Issues										1,549,900
Proceeds from issuance of shares, net										$ 28,200
Maximum shares available to be issued under at the market program										10,000,000
Commissions and offering costs										$ 400
Operating Partnership Units [Member]
Subsidiary, Sale of Stock [Line Items]
Stock issued during period, shares, conversion of units										5,710	133,154	34,075