Consolidated Balance Sheets (Parenthetical) - USD ($) shares in Thousands, $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Investment property, net	$ 5,573,825	$ 5,469,481
Other assets	141,047	146,450
Secured debt	2,822,640	2,819,567
Other liabilities	$ 291,074	$ 279,667
Series A Preferred Stock, Par Value	$ 0.01	$ 0.01
Series A Preferred Stock, Shares Issued	3,400	3,400
Series A Preferred Stock, Shares Outstanding	3,400	3,400
Common Stock, Par Value	$ 0.01	$ 0.01
Common Stock, Shares Authorized	180,000	180,000
Common Stock, Shares Issued	79,341	73,206
Common Stock, Shares Outstanding	79,341	73,206
Series A-4 Preferred Stock
Series A-4 Preferred Stock, Par Value	$ 0.01	$ 0.01
Series A-4 Preferred Stock, Shares Issued	1,085	1,681
Series A-4 Preferred Stock, Shares Outstanding	1,085	1,681
Variable Interest Entity, Primary Beneficiary [Member]
Investment property, net	$ 50,655	$ 88,987
Other assets	1,638	3,054
Secured debt	42,177	62,111
Other liabilities	$ 1,258	$ 1,998