Hotel Management Agreements and Leases - Narrative and Marriott No. 1 (Details) $ in Thousands	3 Months Ended			9 Months Ended
	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($) agreement hotel travelcenter lease_agreement	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($) agreement hotel travelcenter lease_agreement	Sep. 30, 2016 USD ($)
Management Agreements and Leases [Line Items]
Number of operating agreements | agreement		14		14
Capital improvements from leased facilities, funded | $				$ 89,955	$ 122,239
Hotel
Management Agreements and Leases [Line Items]
Number of properties owned | hotel		323		323
Number of operating agreements | lease_agreement		9		9
Number of properties leased to taxable REIT subsidiaries | hotel		320		320
Number of properties leased to third parties | hotel		3		3
Hotel | Marriott No. 1 agreement
Management Agreements and Leases [Line Items]
Number of properties owned | hotel		53		53
Operating agreement annual rent and return | $				$ 69,100
Realized returns and rents | $		$ 17,247	$ 17,126	51,657	51,361
Additional returns realized | $		$ 3,603	$ 4,372	6,807	$ 10,621
Capital improvements from leased facilities, funded | $				$ 4,638
Percentage increase In minimum returns after funding for capital improvements				10.00%
Travel centers
Management Agreements and Leases [Line Items]
Number of properties owned | travelcenter		199		199
Travel centers | TA agreements
Management Agreements and Leases [Line Items]
Number of properties owned | travelcenter		199		199
Number of operating agreements | agreement		5		5
Forecast | Hotel | Marriott No. 1 agreement
Management Agreements and Leases [Line Items]
Capital improvements from leased facilities, funded | $	$ 1,000
Minimum | Hotel
Management Agreements and Leases [Line Items]
Number of real estate properties leased or managed | hotel		1		1
Hotel management agreements and leases, renewal period				20 years
Maximum | Hotel
Management Agreements and Leases [Line Items]
Number of real estate properties leased or managed | hotel		99		99
Hotel management agreements and leases, renewal period				60 years