Debt - Mortgage Notes Payable Narrative (Details) $ in Thousands				12 Months Ended
	Aug. 31, 2017 USD ($) property	Aug. 29, 2017 USD ($) property	Jun. 27, 2017 USD ($) property	Dec. 31, 2017 USD ($) property note_payable	Dec. 31, 2016 USD ($) property	Dec. 31, 2015 USD ($)	Dec. 30, 2016 USD ($) property
Debt Instrument [Line Items]
Gain (loss) on extinguishment and forgiveness of debt, net | $				$ 18,373	$ (771)	$ 4,812
Number of properties secured by each non-recourse loan | property			4	6
Mortgages [Member]
Debt Instrument [Line Items]
Gain (loss) on extinguishment and forgiveness of debt, net | $	$ 6,700	$ 4,800	$ 9,000	$ 300	$ 300
Mortgage notes in connection with default from non-recourse loan | $	$ 41,600	$ 20,500	$ 38,300	$ 16,200			$ 11,600
Number of mortgage notes payable in default | note_payable				1
Number of properties secured by each non-recourse loan | property	1	1
Number of non-recourse loan secured properties | property					2		16