Subsequent Events -Additional Information (Detail)			9 Months Ended
	Oct. 29, 2015 USD ($) a $ / shares	Oct. 08, 2015 ft² a	Sep. 30, 2015 ft² a	Oct. 28, 2015 USD ($)
Subsequent Event [Line Items]
Area of a real estate property | ft²			1,270,000
Tenant contractual right of first refusal to acquire property in advance expired date			Oct. 28, 2015
Due diligence period expiration date			2015-11
Area of land | a			10,500
Subsequent Event [Member]
Subsequent Event [Line Items]
Area of office building acquired | ft²		450,000
Area of a real estate property | a		40
Weighted average remaining lease term		9 years
Acquisition price of real state property				$ 42,300,000
Net proceeds from release of surface entry rights	$ 920,000
Gross proceeds from release of surface entry rights	$ 950,000
Area of land | a	1,400
Impact of gross proceeds surface entry rights in earning per share | $ / shares	$ 0.10