Summary of Significant Accounting Policies - Tax Status of Dividends and Distributions (Details) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accounting Policies [Abstract]
Ordinary dividends (dollars per share)	$ 0	$ 0.4529	$ 0.5325
Qualified REIT dividend (dollars per share)	0.2825	0	0
Qualified dividends (dollars per share)	0	0	0
Capital gain distribution (dollars per share)	0	0	0
Non-dividend distributions (dollars per share)	0.6375	0.4571	0.3675
Total (dollars per share)	$ 0.9200	$ 0.9100	$ 0.9000