Recent Accounting Pronouncements (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred gain on sale of real estate			$ 712
Unrealized gain on investment in equity securities	$ 0	$ 12,142
Equity in earnings of investees	9,712	2,739
Decrease in cash provided by operating activities	(35,267)	(26,225)
Restricted cash	4,766	703	3,111
ASU 2016-01 | Other Comprehensive Income (Loss)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Unrealized gain on investment in equity securities			45,116
ASU 2016-15
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accretion in equity of earnings	$ (736)
ASU 2016-18
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Decrease in cash provided by operating activities		$ 173
Equity Method Investee, Select Income REIT, or SIR | ASU 2016-01 | Other Comprehensive Income (Loss)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Equity in earnings of investees			$ 14,325