Financial Highlights (Results of Operations for a Share Outstanding) (Details) - $ / shares	3 Months Ended	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2018	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017
Increase (Decrease) Equity Per Share [Roll Forward]
Beginning Shareholders' Equity Per Share (3/31/2018 and 12/31/2017, respectively)	$ 19.56	$ 19.15
Net Investment Income	0.36	0.70
Net Realized/Unrealized Gains (Losses)	0.37	0.72
Results of Operations Attributable to Equity	0.73	1.42
Less: Results of Operations Attributable to Non-controlling Interests	(0.03)	(0.04)
Results of Operations Attributable to Shareholders' Equity	0.70	1.38
Dividends Paid to Common Shareholders	(0.41)	(0.82)
Weighted Average Share Impact on Dividends Paid	(0.01)	(0.02)
Accretive (Dilutive) Effect of Share Issuances (Net of Offering Costs), Share Repurchases, and Adjustments to Non-controlling Interest	0.05	0.20
Ending Shareholders' Equity Per Share (3/31/2018 and 3/31/2017, respectively)	$ 19.89	$ 19.89
Shares Outstanding, end of period	30,149,880	30,149,880	29,745,776	29,745,776	29,796,601	30,392,041	31,335,938
Shareholders Equity Per Share Upon Conversion Of All Convertible Units (in usd per share)	$ 19.57	$ 19.57