Net Income Per Share and Equity - Narratives (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Distributions Declared
Interest expense	$ 12,930	$ 11,452
Dividends payment	Apr. 16, 2018
Distributions payable	$ 21,834		$ 21,686
Class A
Distributions Declared
Interest expense	$ 100	$ 100
Distributions declared per share (in dollars per share)	$ 0.1563	$ 0.1563
Class C
Distributions Declared
Distributions declared per share (in dollars per share)	$ 0.1375	$ 0.1380