Summary of Acquisitions of Real Estate Held for Investment (Detail) - USD ($) $ in Thousands		1 Months Ended		9 Months Ended	12 Months Ended
		Aug. 31, 2015	Jul. 31, 2015	Sep. 30, 2015	Dec. 31, 2014
Transaction to Real Estate Investments [Line Items]
Purchase Price				$ 29,900	$ 190,743
OHIO
Transaction to Real Estate Investments [Line Items]
Purchase Price				$ 11,000
OHIO | Multi Tenant Properties [Member]
Transaction to Real Estate Investments [Line Items]
Date of Acquisition				Jul. 31, 2015
Purchase Price				$ 11,000
Remaining Lease Term (Years)	[1]			5 years 1 month 6 days
OHIO | Single Tenant Properties [Member]
Transaction to Real Estate Investments [Line Items]
Purchase Price			$ 11,000
FLORIDA
Transaction to Real Estate Investments [Line Items]
Purchase Price				$ 18,900
FLORIDA | Multi Tenant Properties [Member]
Transaction to Real Estate Investments [Line Items]
Date of Acquisition				Aug. 31, 2015
Purchase Price		$ 18,900		$ 18,900
Remaining Lease Term (Years)	[1]			4 years 4 months 24 days
TENNESSEE
Transaction to Real Estate Investments [Line Items]
Purchase Price					19,000
TENNESSEE | Single Tenant Properties [Member]
Transaction to Real Estate Investments [Line Items]
Date of Acquisition				Apr. 30, 2014
Purchase Price				$ 19,000
Remaining Lease Term (Years)	[1]			8 years
VIRGINIA
Transaction to Real Estate Investments [Line Items]
Purchase Price					$ 17,743
VIRGINIA | Multi Tenant Properties [Member]
Transaction to Real Estate Investments [Line Items]
Date of Acquisition				Jun. 30, 2014
Purchase Price				$ 17,743
Remaining Lease Term (Years)	[1]			7 years
New York, Ohio and Georgia [Member] | Multi Tenant Properties [Member]
Transaction to Real Estate Investments [Line Items]
Date of Acquisition				Nov. 30, 2014
Purchase Price				$ 154,000
Remaining Lease Term (Years)	[1]			4 years 7 months 6 days

[1] Does not include extension options.