Equity Investment in Select Income REIT (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Schedule of Equity Method Investments [Line Items]
Equity in earnings of investees	$ 2,739	$ 9,934
Investment at carrying value	482,103		$ 487,708
Cash distributions from SIR	$ 1,875	9,117
SIR
Schedule of Equity Method Investments [Line Items]
Equity investments, common shares owned (in shares)	24,918,421
Percentage of outstanding shares owned	27.90%
Equity in earnings of investees	$ 2,611	9,857
Equity in unrealized gain (loss) of investees	4,492	4,492
The amount of investment in exceed the underlying equity of the investee	89,449
Accretion in equity of earnings	736	740
Investment at carrying value	482,103
Equity Investments, market value	642,646
Cash distributions from SIR	$ 12,708	$ 12,459