Supplemental Detail for Certain Components of Consolidated Balance Sheets - Distributions Payable (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Distributions payable
Distributions payable	$ 64,399	$ 60,799
Noncontrolling interests
Distributions payable
Distributions payable	158	86
Common stock
Distributions payable
Distributions payable	$ 64,241	$ 60,713