Summary of Significant Accounting Policies - Dividends and Distributions (Details) - $ / shares													12 Months Ended
	Dec. 21, 2018	Sep. 19, 2018	Jun. 21, 2018	Mar. 23, 2018	Dec. 21, 2017	Sep. 21, 2017	Jun. 12, 2017	Mar. 17, 2017	Dec. 22, 2016	Sep. 26, 2016	Jun. 23, 2016	Apr. 18, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accounting Policies [Abstract]
Dividends and distributions declared per common share and unit (in dollars per share)	$ 0.230	$ 0.230	$ 0.230	$ 0.230	$ 0.230	$ 0.230	$ 0.230	$ 0.225	$ 0.225	$ 0.225	$ 0.225	$ 0.225	$ 0.920	$ 0.915	$ 0.900