Distributions Paid and Payable - Tax Characterization of Distributions Paid (Details) - $ / shares	1 Months Ended																																				3 Months Ended								12 Months Ended
	Dec. 31, 2019	Nov. 30, 2019	Oct. 31, 2019	Sep. 30, 2019	Aug. 31, 2019	Jul. 31, 2019	Jun. 30, 2019	May 31, 2019	Apr. 30, 2019	Mar. 31, 2019	Feb. 28, 2019	Jan. 31, 2019	Dec. 31, 2018	Nov. 30, 2018	Oct. 31, 2018	Sep. 30, 2018	Aug. 31, 2018	Jul. 31, 2018	Jun. 30, 2018	May 31, 2018	Apr. 30, 2018	Mar. 31, 2018	Feb. 28, 2018	Jan. 31, 2018	Dec. 31, 2017	Nov. 30, 2017	Oct. 31, 2017	Sep. 30, 2017	Aug. 31, 2017	Jul. 31, 2017	Jun. 30, 2017	May 31, 2017	Apr. 30, 2017	Mar. 31, 2017	Feb. 28, 2017	Jan. 31, 2017	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Class of Stock [Line Items]
Totals (in dollars per share)	$ 0.2270	$ 0.2270	$ 0.2270	$ 0.2265	$ 0.2265	$ 0.2265	$ 0.2260	$ 0.2260	$ 0.2260	$ 0.2255	$ 0.2255	$ 0.2210	$ 0.2205	$ 0.2205	$ 0.2205	$ 0.2200	$ 0.2200	$ 0.2200	$ 0.2195	$ 0.2195	$ 0.2195	$ 0.2190	$ 0.2190	$ 0.2125	$ 0.2120	$ 0.2120	$ 0.2120	$ 0.2115	$ 0.2115	$ 0.2115	$ 0.2110	$ 0.2110	$ 0.2110	$ 0.2105	$ 0.2105	$ 0.2025	$ 0.6810	$ 0.6795	$ 0.6780	$ 0.6720	$ 0.6615	$ 0.6600	$ 0.6585	$ 0.6505	$ 2.7105	$ 2.6305	$ 2.5270
Common stock
Class of Stock [Line Items]
Distributions characterized as ordinary income (in dollars per share)																																													2.1206964	2.0269173	1.9402085
Distributions characterized as nontaxable distributions (in dollars per share)																																													0.5898036	0.6035827	0.5478464
Total capital gain distribution (in dollars per share)																																													0	0	0.0389451
Totals (in dollars per share)																																													$ 2.7105000	$ 2.6305000	$ 2.5270000