Related Party Transactions (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		0 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Mar. 12, 2015	Dec. 31, 2014	Dec. 31, 2013 item	Dec. 31, 2010	Sep. 30, 2010	Dec. 31, 2007 property
Summary of details amounts related to the HPT Leases and other leases that are reflected in real estate rent expense in condensed consolidated statements of income and comprehensive income
Less sale-leaseback financing obligation amortization	$ (636)	$ (589)
Rent paid to others	2,621	2,685
Adjustments to recognize expense on a straight line basis for other leases	(101)	(57)
Total real estate rent expense	55,604	54,204
Current HPT Leases liabilities:
Total Current HPT Leases liabilities	31,785			31,637
Noncurrent HPT Leases liabilities:
Total Noncurrent HPT Lease liabilities	330,290			332,934
Other related party transactions
Income (loss ) recognized related to equity investments	791	254
Business management and shared services | RMR
Other related party transactions
Period before which written notice is required to be given for termination of business management agreement			120 days
HPT
Related Party Transactions
Number of common shares owned	3,420,000
Percentage of outstanding common shares owned	8.90%
Number of leases	2
Increase to annual rent payable	1,715
Summary of details amounts related to the HPT Leases and other leases that are reflected in real estate rent expense in condensed consolidated statements of income and comprehensive income
Cash payments for rent under the HPT Leases	57,516	55,146
Change in accrued estimated percentage rent	(104)	618
Adjustments to recognize expense on a straight line basis	(452)	(341)
Less sale-leaseback financing obligation amortization	(636)	(589)
Less portion of rent payments recognized as interest expense	(1,452)	(1,470)
Less deferred tenant improvements allowance amortization	(1,692)	(1,692)
Amortization of deferred gain on sale-leaseback transactions	(96)	(96)
Rent expense related to HPT Leases	53,084	51,576
Current HPT Leases liabilities:
Accrued rent	19,473			19,407
Sale-leaseback financing obligation	2,619			2,547
Straight line rent accrual	2,539			2,529
Deferred gain on sale-leaseback transactions	385			385
Deferred tenant improvements allowance	6,769			6,769
Total Current HPT Leases liabilities	31,785			31,637
Noncurrent HPT Leases liabilities:
Deferred rent obligation	150,000			150,000		150,000
Sale-leaseback financing obligation	82,374			82,591
Straight line rent accrual	49,595			50,234
Deferred gain on sale-leaseback transactions	2,636			2,732
Deferred tenant improvements allowance	45,685			47,377
Total Noncurrent HPT Lease liabilities	330,290			332,934
Annual percentage rent recognized as an expense	1,193	893
Improvements sold	20,181
Improvements included in property and equipment	29,927
Increase to annual rent payable	1,715
Other related party transactions
Number of real estate properties not qualifying for operating lease treatment					5
Less portion of rent payments recognized as interest expense	(1,452)	(1,470)
Number of installments in which deferred rent is payable	2
HPT | Deferred rent obligation payable in December 2022
Noncurrent HPT Leases liabilities:
Deferred rent obligation	107,085
HPT | Deferred rent obligation payable in June 2024
Noncurrent HPT Leases liabilities:
Deferred rent obligation	42,915
HPT | TA Lease
Related Party Transactions
Number of properties under lease	144
Other related party transactions
Number of real estate properties leased to be recognized	8							13
Number of real estate properties not qualifying for operating lease treatment	1
The term of scheduled rent increase from the initial lease term	6 years
Amount funded for leasehold improvements							125,000
HPT | Petro Lease
Related Party Transactions
Number of properties under lease	40
Percentage rent to be waived	2,500
Percentage rent waived	259	152
Cumulative percentage rent waived	1,266
AIC
Other related party transactions
Equity method investments, carrying value	6,945
Income (loss ) recognized related to equity investments	72	(97)
PTP
Other related party transactions
Equity method investments, carrying value	21,526
Income (loss ) recognized related to equity investments	719	351
Management and accounting fee income recognized	200	200
Net payable	1,041
RMR
Other related party transactions
Aggregate fees	$ 3,495	$ 2,893
RMR | Business management and shared services
Other related party transactions
Period before which written notice is required to be given for termination of business management agreement			60 days
Multiple in calculating termination fee			2.875
Period over which base management fee is determined as basis to calculate termination fee			24 months
Business Management Agreement, Termination, Transition Period			120 days