Management Agreements and Leases - Narrative and Marriott No. 1 (Details) $ in Thousands	3 Months Ended			9 Months Ended
	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($) Agreement agreement hotel travelcenter property	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($) Agreement agreement hotel travelcenter property	Sep. 30, 2017 USD ($)
Management Agreements and Leases [Line Items]
Number of operating agreements | agreement		13		13
Capital improvements from leased facilities, funded				$ 111,248	$ 89,955
Hotel
Management Agreements and Leases [Line Items]
Number of properties owned | hotel		325		325
Number of operating agreements | Agreement		8		8
Number of properties leased to taxable REIT subsidiaries | hotel		323		323
Number of properties leased to third parties | hotel		2		2
Hotel | Marriott No. 1 agreement
Management Agreements and Leases [Line Items]
Number of properties owned | hotel		53		53
Operating agreement annual rent and return				$ 69,409
Realized returns and rents		$ 17,335	$ 17,247	51,954	51,657
Additional returns realized		$ 2,584	$ 3,603	5,113	$ 6,807
Capital improvements from leased facilities, funded				$ 1,769
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
Forecast | Hotel | Marriott No. 1 agreement
Management Agreements and Leases [Line Items]
Capital improvements from leased facilities, funded	$ 8,200
Minimum | Hotel
Management Agreements and Leases [Line Items]
Number of real estate properties leased or managed | property		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		100		100
Hotel management agreements and leases, renewal period				60 years