CONDENSED CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Shares	Additional Paid-in Capital	Cumulative Net Income	Cumulative Other Comprehensive Income (Loss)	Cumulative Distributions	Total Equity Attributable to Common Shareholders	Total Equity Attributable to Noncontrolling Interest	Five Star Shareholders	Five Star Shareholders Cumulative Distributions	Five Star Shareholders Total Equity Attributable to Common Shareholders
Beginning balance (in shares) at Dec. 31, 2018		237,729,900
Beginning balance at Dec. 31, 2018	$ 3,179,870	$ 2,377	$ 4,611,419	$ 2,140,796	$ (266)	$ (3,731,214)	$ 3,023,112	$ 156,758
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income	31,504			30,082			30,082	1,422
Other comprehensive income	66				66		66
Distributions	(92,714)					(92,714)	(92,714)
Share grants	215		215				215
Distributions to noncontrolling interest	(5,503)							(5,503)
Ending balance (in shares) at Mar. 31, 2019		237,729,900
Ending balance at Mar. 31, 2019	3,113,438	$ 2,377	4,611,634	2,170,878	(200)	(3,823,928)	2,960,761	152,677
Beginning balance (in shares) at Dec. 31, 2018		237,729,900
Beginning balance at Dec. 31, 2018	3,179,870	$ 2,377	4,611,419	2,140,796	(266)	(3,731,214)	3,023,112	156,758
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income	(4,312)
Other comprehensive income	137
Ending balance (in shares) at Jun. 30, 2019		237,740,761
Ending balance at Jun. 30, 2019	3,036,709	$ 2,377	4,611,993	2,133,649	(129)	(3,859,587)	2,888,303	148,406
Beginning balance (in shares) at Mar. 31, 2019		237,729,900
Beginning balance at Mar. 31, 2019	3,113,438	$ 2,377	4,611,634	2,170,878	(200)	(3,823,928)	2,960,761	152,677
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income	(35,816)			(37,229)			(37,229)	1,413
Other comprehensive income	71				71		71
Distributions	(35,659)					(35,659)	(35,659)
Share grants (in shares)		15,000
Share grants	395		395				395
Share repurchases (in shares)		(4,139)
Share repurchases	(36)		(36)				(36)
Distributions to noncontrolling interest	(5,684)							(5,684)
Ending balance (in shares) at Jun. 30, 2019		237,740,761
Ending balance at Jun. 30, 2019	$ 3,036,709	$ 2,377	4,611,993	2,133,649	(129)	(3,859,587)	2,888,303	148,406
Beginning balance (in shares) at Dec. 31, 2019	237,897,163	237,897,163
Beginning balance at Dec. 31, 2019	$ 2,877,050	$ 2,379	4,612,511	2,052,562	0	(3,930,933)	2,736,519	140,531
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income	11,143			9,735			9,735	1,408
Distributions	(35,684)					(35,684)	(35,684)
Distribution to common shareholders of the right to receive Five Star Senior Living Inc. common stock									$ (59,801)	$ (59,801)	$ (59,801)
Share grants	249		249				249
Share repurchases (in shares)		(3,438)
Share repurchases	(21)		(21)				(21)
Distributions to noncontrolling interest	(5,767)							(5,767)
Ending balance (in shares) at Mar. 31, 2020		237,893,725
Ending balance at Mar. 31, 2020	$ 2,787,169	$ 2,379	4,612,739	2,062,297	0	(4,026,418)	2,650,997	136,172
Beginning balance (in shares) at Dec. 31, 2019	237,897,163	237,897,163
Beginning balance at Dec. 31, 2019	$ 2,877,050	$ 2,379	4,612,511	2,052,562	0	(3,930,933)	2,736,519	140,531
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income	(13,599)
Other comprehensive income	$ 0
Distribution to common shareholders of the right to receive Five Star Senior Living Inc. common stock									$ (59,801)
Ending balance (in shares) at Jun. 30, 2020	237,951,968	237,951,968
Ending balance at Jun. 30, 2020	$ 2,754,840	$ 2,380	4,613,146	2,036,225	0	(4,028,797)	2,622,954	131,886
Beginning balance (in shares) at Mar. 31, 2020		237,893,725
Beginning balance at Mar. 31, 2020	2,787,169	$ 2,379	4,612,739	2,062,297	0	(4,026,418)	2,650,997	136,172
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income	(24,742)			(26,072)			(26,072)	1,330
Other comprehensive income	0
Distributions	(2,379)					(2,379)	(2,379)
Share grants (in shares)		60,000
Share grants	416	$ 1	415				416
Share repurchases (in shares)		(1,757)
Share repurchases	(8)		(8)				(8)
Distributions to noncontrolling interest	$ (5,616)							(5,616)
Ending balance (in shares) at Jun. 30, 2020	237,951,968	237,951,968
Ending balance at Jun. 30, 2020	$ 2,754,840	$ 2,380	$ 4,613,146	$ 2,036,225	$ 0	$ (4,028,797)	$ 2,622,954	$ 131,886