Distributions Paid and Payable - Distributions to Common Stockholders (Details) - $ / shares	1 Months Ended													6 Months Ended
	Jul. 31, 2019	Jun. 30, 2019	May 31, 2019	Apr. 30, 2019	Mar. 31, 2019	Feb. 28, 2019	Jan. 31, 2019	Jun. 30, 2018	May 31, 2018	Apr. 30, 2018	Mar. 31, 2018	Feb. 28, 2018	Jan. 31, 2018	Jun. 30, 2019	Jun. 30, 2018
Distributions Paid and Payable
Distributions paid per common share (in dollars per share)		$ 0.2260	$ 0.2260	$ 0.2260	$ 0.2255	$ 0.2255	$ 0.2210	$ 0.2195	$ 0.2195	$ 0.2195	$ 0.2190	$ 0.2190	$ 0.2125	$ 1.3500	$ 1.3090
Distributions payable (in dollars per share)		$ 0.2265												$ 0.2265
Subsequent event
Distributions Paid and Payable
Distributions paid per common share (in dollars per share)	$ 0.2265