Fair Value of Assets and Liabilities Recurring and Non-Recurring (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2016 USD ($) shares
Travel Centers of America LLC
Fair Value of Assets and Liabilities
Shares included in investment securities | shares	3,420,000
Unrealized gain (loss) on securities included in cumulative other comprehensive income	$ 5,746
RMR Inc
Fair Value of Assets and Liabilities
Unrealized gain (loss) on securities included in cumulative other comprehensive income	$ 3,755
Quoted Prices in Active Markets for Identical Assets (Level 1) | Travel Centers of America LLC
Fair Value of Assets and Liabilities
Shares included in investment securities | shares	3,420,000
Historical cost of securities	$ 17,407
Quoted Prices in Active Markets for Identical Assets (Level 1) | RMR Inc
Fair Value of Assets and Liabilities
Shares included in investment securities | shares	2,503,777
Historical cost of securities	$ 66,374
Recurring | Travel Centers of America LLC
Fair Value of Assets and Liabilities
Investment securities	23,153
Recurring | RMR Inc
Fair Value of Assets and Liabilities
Investment securities	62,619
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Travel Centers of America LLC
Fair Value of Assets and Liabilities
Investment securities	23,153
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | RMR Inc
Fair Value of Assets and Liabilities
Investment securities	$ 62,619