Supplemental Detail for Certain Components of Consolidated Balance Sheets - Distributions Payable (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Distributions payable
Declared distributions	$ 54,768	$ 50,344
Noncontrolling interests
Distributions payable
Declared distributions	82	124
Common stock
Distributions payable
Declared distributions	52,429	47,963
Preferred stock
Distributions payable
Declared distributions	$ 2,257	$ 2,257