Real Estate, Operating Real Estate, and Assets Held for Sale - Net Assets Acquired (Details) - USD ($) $ in Thousands		12 Months Ended
	Oct. 03, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Assets
Other assets, net		$ 322,201	$ 228,717
Total assets		4,587,470	4,698,923
Liabilities
Total liabilities		2,244,213	2,383,919
Noncontrolling interest contribution		(107,861)	(97,494)
Net cash received		119,094	273,635	$ 152,889	$ 275,719
(Loss) gain on change in control of interests		$ (13,851)	$ 49,922	$ 0
Shelborne
Assets
Land	$ 34,397
Buildings and improvements	46,261
Other assets, net	32,695
Total assets	113,353
Liabilities
Other Liabilities	2,777
Total liabilities	2,777
Total identifiable net assets	110,576
Noncontrolling interest contribution	(9,529)
Net cash received	3,829
Fair value of our majority interest in investment	104,876
Carrying value of previously held equity investment	(118,727)
(Loss) gain on change in control of interests	$ (13,851)