Business and Property Management Agreements with RMR LLC (Details)	1 Months Ended	3 Months Ended		6 Months Ended
	Jan. 31, 2019 USD ($)	Jun. 30, 2019 USD ($) employee	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($) management_agreement employee	Jun. 30, 2018 USD ($)
Related person transactions
Number of employees | employee		0		0
Related party transaction business management agreement incentive fee paid	$ 40,642,000
Property management and construction supervision fees		$ 3,491,000	$ 2,984,000	$ 6,555,000	$ 5,805,000
Property management and construction supervision fees paid		3,352,000	3,172,000	6,726,000	5,951,000
RMR LLC
Related person transactions
Business management fees incurred		6,582,000	26,489,000	14,301,000	49,813,000
Related party transaction business management fees related to subsidiary level management		725,000	725,000	1,450,000	1,450,000
Related party transaction business management agreement, annual incentive fee estimate included in management fees		$ 0	$ 17,610,000	$ 0	$ 31,957,000
Senior Living Communities | RMR Inc
Related person transactions
Number of consecutive renewal terms of agreement | management_agreement				2