Fair Value of Assets and Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Assets and liabilities measured at fair value
Senior unsecured notes	$ 1,723,484	$ 1,722,758
Carrying value
Assets and liabilities measured at fair value
Senior unsecured notes	1,723,484	1,722,758
Secured Debt	1,103,518	1,106,183
Debt Instrument	2,827,002	2,828,941
Fair value
Assets and liabilities measured at fair value
Senior unsecured notes	1,806,912	1,755,715
Secured Debt	1,101,363	1,090,515
Debt Instrument	$ 2,908,275	$ 2,846,230
Five Star
Assets and liabilities measured at fair value
Investment in common shares (in shares)	4,235,000
Five Star \| Common Shares
Assets and liabilities measured at fair value
Investment in common shares (in shares)	4,235,000
RMR Inc \| Class A common shares
Assets and liabilities measured at fair value
Investment in common shares (in shares)	2,637,408
Recurring
Assets and liabilities measured at fair value
Investments in available for sale securities	$ 139,657
Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets and liabilities measured at fair value
Investments in available for sale securities	139,657
Recurring \| Significant Unobservable Inputs (Level 3)
Assets and liabilities measured at fair value
Investments in available for sale securities	$ 0

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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Fair value portion of debt instrument payable, including, but not limited to, notes payable and loans payable.

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Balance held at close of period in number of shares.

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Carrying value as of the balance sheet date, including the current and noncurrent portions, of collateralized debt obligations (with maturities initially due after one year or beyond the operating cycle, if longer). Such obligations include mortgage loans, chattel loans, and any other borrowings secured by assets of the borrower.

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Including the current and noncurrent portions, carrying value as of the balance sheet date of Notes with the highest claim on the assets of the issuer in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle if longer). Senior note holders are paid off in full before any payments are made to junior note holders.

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