Financial Highlights (Expense Ratios To Average Equity) (Details)		3 Months Ended		6 Months Ended
		Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Investment Company, Financial Highlights [Abstract]
Operating expenses, before interest expense and other investment related expenses	[1],[2]	(3.01%)	(2.83%)	(2.84%)	(2.83%)
Incentive fee	[1],[2]	(0.05%)	(0.00%)	(0.05%)	(0.00%)
Interest expense and other investment related expenses	[1],[2]	(11.23%)	(6.02%)	(10.39%)	(5.37%)
Total Expenses	[1],[2]	(14.29%)	(8.85%)	(13.28%)	(8.20%)

[1] Average equity is calculated using month end values.

[2] Ratios are annualized except for the incentive fee which is not annualized.