Fair Value of Assets and Liabilities (Details) (USD $) In Thousands, except Share data, unless otherwise specified	9 Months Ended
	Sep. 30, 2013 item	Sep. 30, 2012	Dec. 31, 2012
Assets and liabilities measured at fair value
Number of properties classified as held for sale	19
Cumulative impairments of properties held for sale	$ 38,005
Number of properties in long-lived assets held and used	1
Impairment of assets charge related to long-lived assets held and used	1,304	3,071
Number of public issues of unsecured senior notes	4
Senior notes	1,093,016		1,092,053
Excess of fair value over aggregate book value	9,181
CommonWealth REIT (CWH)
Assets and liabilities measured at fair value
Investment in common shares	250,000
Five Star
Assets and liabilities measured at fair value
Investment in common shares	4,235,000
Recurring and Nonrecurring | Total
Assets and liabilities measured at fair value
Assets held for sale	94,891
Long-lived assets held and used	653
Investments in available for sale securities	27,372
Unsecured senior notes	1,102,198
Secured debt	764,495
Recurring and Nonrecurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets and liabilities measured at fair value
Investments in available for sale securities	27,372
Unsecured senior notes	1,102,198
Recurring and Nonrecurring | Significant Other Observable Inputs (Level 2)
Assets and liabilities measured at fair value
Assets held for sale	94,891
Long-lived assets held and used	653
Recurring and Nonrecurring | Significant Unobservable Inputs (Level 3)
Assets and liabilities measured at fair value
Secured debt	$ 764,495