Supplemental Detail for Certain Components of Consolidated Balance Sheets - Distributions Payable (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Distributions payable
Distributions payable	$ 60,799	$ 55,235
Noncontrolling interests
Distributions payable
Distributions payable	86	82
Common stock
Distributions payable
Distributions payable	$ 60,713	52,896
Preferred stock
Distributions payable
Distributions payable		$ 2,257