Summary of Significant Accounting Policies (Detail)		3 Months Ended
	Jul. 01, 2016 USD ($) a extension	Mar. 31, 2017 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Cash and cash equivalents		$ 11,676,000		$ 15,525,000
Restricted cash		6,537,000		0
Cash, cash equivalents and restricted cash, end of period		$ 18,213,000	$ 6,402,000	15,525,000	$ 5,201,000
Allocation period		1 year
Interest capitalized		$ 466,000	439,000
Real estate taxes and insurance costs capitalized		$ 300,000	200,000
REIT annual taxable income distribution requirement percentage		90.00%
Income tax provision		$ 0	0
Rents and other receivables		5,109,000		5,565,000
Allowance for doubtful accounts		(2,188,000)		(2,816,000)
Rents and other receivables, net		2,921,000		2,749,000
Deferred rent receivable		12,844,000		11,903,000
Allowance for doubtful accounts		(51,000)		(30,000)
Deferred rent receivable, net		12,793,000		$ 11,873,000
Provision for doubtful accounts		$ 326,000	465,000
Minimum
Summary Of Significant Accounting Policies [Line Items]
Fair value inputs, discount rate		9.50%
Fair value inputs, capitalization rate		7.50%
Minimum | Building
Summary Of Significant Accounting Policies [Line Items]
Estimated remaining life		10 years
Minimum | Site Improvements
Summary Of Significant Accounting Policies [Line Items]
Estimated remaining life		5 years
Maximum | Building
Summary Of Significant Accounting Policies [Line Items]
Estimated remaining life		30 years
Maximum | Site Improvements
Summary Of Significant Accounting Policies [Line Items]
Estimated remaining life		20 years
Construction Employees
Summary Of Significant Accounting Policies [Line Items]
Compensation costs capitalized		$ 400,000	200,000
Leasing Employees
Summary Of Significant Accounting Policies [Line Items]
Compensation costs capitalized		200,000	$ 100,000
Rancho Cucamonga, CA
Summary Of Significant Accounting Policies [Line Items]
Mortgage loan, face amount	$ 6,000,000	6,000,000
Rentable square feet | a	64,965
Proceeds from fees received	$ 300,000
Interest rate	10.00%
Number of extensions | extension	1
Extension term	6 months
Deferred interest	$ 14,000
Mortgage loans, carrying amount		6,100,000
Accrued interest		200,000
Unamortized origination fee		$ 100,000