Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($)	1 Months Ended	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Significant Accounting Policies [Line Items]
Federal Deposit Insurance Corporation deposit insurance limit per institution	$ 250,000	$ 250,000		$ 250,000
Restricted cash	6,441,000	6,441,000		$ 6,441,000		$ 4,864,000
Acquisition of above-market in-place leases, amortization period				6 months
Amortization expense for intangible assets		439,000	$ 186,000	$ 835,000	$ 557,000
Write-off of fully amortized intangible assets		792,000	503,000	792,000	950,000
Additional amortization expense on current in-place intangible assets for the remainder of 2021	714,000	714,000		714,000
Depreciation expense		16,324,000	15,045,000	32,480,000	29,502,000
Casualty losses		0	411,000	359,000	411,000
Investments in joint ventures	10,205,000	10,205,000	0	10,205,000	0
Income or losses from equity method investments		0	0	0	0
Bad debt expense		590,000	751,000	1,023,000	1,088,000
Deferred rent receivable from residents	12,000	12,000		12,000
Advertising expenses		636,000	551,000	1,180,000	1,160,000
Transfers of assets between Level 1 and Level 2	0	0		0
Transfers of assets between Level 2 and Level 1	0	0		0
Transfers of liabilities between Level 1 and Level 2	0	0		0
Transfers of liabilities between Level 2 and Level 1	0	0		0
Income tax expense		0	0	$ 0	0
Percentage of minimum taxable income distributable to stockholders				90.00%
Subsequent disqualification period if failed to qualify as REIT				4 years
Topic 842
Significant Accounting Policies [Line Items]
Right-of-use assets	$ 2,457,000	$ 2,457,000		$ 2,457,000
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	Other assets	Other assets		Other assets
Lease liability	$ 2,803,000	$ 2,803,000		$ 2,803,000
Operating Lease, Liability, Statement of Financial Position [Extensible List]	Other liabilities	Other liabilities		Other liabilities
Total operating lease expense		$ 166,000		$ 338,000
Natural Disasters and Other Insurable Events
Significant Accounting Policies [Line Items]
Rent revenue recognized		19,000	$ 148,000	41,000	$ 151,000
COVID-19
Significant Accounting Policies [Line Items]
Bad debt expense		78,000		125,000
Building and Building Improvements
Significant Accounting Policies [Line Items]
Depreciable Lives	40 years
Leases Acquired In Place
Significant Accounting Policies [Line Items]
Acquisition of above-market in-place leases		$ 757,000		$ 757,000
Minimum
Significant Accounting Policies [Line Items]
Percentage of rent deferment on monthly rent				25.00%
Deferred rent payment term				1 month
Minimum | Equipment and Fixtures
Significant Accounting Policies [Line Items]
Depreciable Lives				5 years
Maximum
Significant Accounting Policies [Line Items]
Cash and cash equivalents maturity period				3 months
Percentage of rent deferment on monthly rent				75.00%
Deferred rent payment term				3 months
Maximum | Topic 842
Significant Accounting Policies [Line Items]
Operating lease term	10 years	10 years		10 years
Maximum | Equipment and Fixtures
Significant Accounting Policies [Line Items]
Depreciable Lives				10 years