Fair Value Measurements - Summary of the Face Value, Carrying Amount and Fair Value of Financial Instruments (Detail) - USD ($)	Jun. 30, 2017	Dec. 31, 2016
Financial assets:
Preferred equity investment - face value	$ 4,531,000	$ 12,031,000
Preferred equity investment	5,200,000
Financial liabilities:
Senior unsecured notes payable, net	294,043,000	255,294,000
Senior unsecured notes payable | Level 2
Financial liabilities:
Financial liabilities - face value	300,000,000	260,000,000
Carrying Amount
Financial assets:
Preferred equity investment	5,192,000	13,872,000
Carrying Amount | Level 2
Financial liabilities:
Senior unsecured notes payable, net	294,043,000	255,294,000
Fair Value
Financial assets:
Preferred equity investment	5,066,000	14,289,000
Fair Value | Level 2
Financial liabilities:
Senior unsecured notes payable, net	$ 308,250,000	$ 265,850,000