Summary of Significant Accounting Policies - Narrative (Detail) $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended
	Aug. 31, 2021	Sep. 30, 2021 USD ($) seniorHousingCommunity shares	Sep. 30, 2020 USD ($) seniorHousingCommunity shares	Sep. 30, 2021 USD ($) seniorHousingCommunity shares	Sep. 30, 2020 USD ($) seniorHousingCommunity shares	Dec. 31, 2020 USD ($)
Accounting Policies [Line Items]
Debt service reserve		$ 5,882	$ 3,982	$ 5,882	$ 3,982	$ 4,982
Resident revenue		57,924	$ 96,053	177,114	$ 303,659
Contract liabilities for deferred fees paid		447		$ 447		822
Resident receivables due period				30 days
Allowance for doubtful accounts		$ 5,100		$ 5,100		6,100
Number of senior housing communities | seniorHousingCommunity		72		72
BBVA USA | Notes payable, noncompliance
Accounting Policies [Line Items]
Term of extension	1 year
Debt service reserve		$ 900		$ 900
Consolidated Properties | TEXAS
Accounting Policies [Line Items]
Number of senior housing communities | seniorHousingCommunity		16	38	16	38
Unvested Restricted Stock and Restricted Stock Units
Accounting Policies [Line Items]
Antidilutive shares excluded from earnings per share (in shares) | shares		65,118	45,667	65,118	45,667
Stock Options
Accounting Policies [Line Items]
Antidilutive shares excluded from earnings per share (in shares) | shares		9,816	9,800	9,816	9,800
Rental and Other Services
Accounting Policies [Line Items]
Resident revenue		$ 48,200	$ 84,700	$ 138,700	$ 286,100
Housing And Support Services
Accounting Policies [Line Items]
Contract liabilities for deferred fees paid		2,700		2,700		3,300
Ancillary Services
Accounting Policies [Line Items]
Resident revenue		300	100	900	1,600
Community Fees
Accounting Policies [Line Items]
Resident revenue		400	1,000	1,200	3,200
Contract liabilities for deferred fees paid		800		800		$ 900
Management fees
Accounting Policies [Line Items]
Resident revenue		1,029	604	2,978	819
Community reimbursement revenue
Accounting Policies [Line Items]
Resident revenue		$ 7,927	$ 9,555	$ 33,317	$ 11,888