Stockholders' Equity / Partners' Capital - Summary of Equity Program Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2017	Jun. 30, 2016
Class of Stock [Line Items]
Total net proceeds		$ 189,757	$ 740,025
ATM Equity Program
Class of Stock [Line Items]
Total net proceeds	$ 124,745	187,403
Commissions paid to sales agents	$ 1,573	$ 2,354
Weighted average price per share (in dollars per share)	$ 47.69	$ 48.34
Shares of common stock sold (in shares)	2,648,735	3,925,456