Real Estate Investments - Additional Information (Detail) (USD $)	0 Months Ended	3 Months Ended		9 Months Ended			0 Months Ended		9 Months Ended				0 Months Ended	9 Months Ended
	Jul. 30, 2014	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013	Oct. 02, 2014 Subsequent Event [Member]	Jan. 17, 2014 Liberty Apartments [Member]	Sep. 30, 2014 Liberty Apartments [Member]	Jan. 17, 2014 Liberty Apartments [Member]	Sep. 30, 2014 Virginia Beach, VA [Member]	Sep. 29, 2014 Virginia Beach, VA [Member]	Aug. 15, 2014 Dimmock Square [Member]	Sep. 30, 2014 Dimmock Square [Member]	Aug. 15, 2014 Dimmock Square [Member] sqft	Sep. 30, 2014 Williamsburg VA [Member]	Apr. 16, 2014 Williamsburg VA [Member]	May 01, 2014 Chesapeake VA [Member]
Real Estate Properties [Line Items]
Acquisition, total consideration								$ 26,700,000					$ 19,700,000
Acquisition, common units issued								695,652					990,952
Acquisition, assumption of debt								17,000,000
Acquisition, cash consideration								3,000,000
Fair value adjustment to the assumed debt								1,500,000
Outstanding principal balance of the assumed debt									16,966,000	18,500,000
Acquisition date									Jan. 17, 2014					Aug. 15, 2014
Rental revenues		16,713,000	14,899,000	47,225,000	42,528,000				600,000					300,000
Net income (loss)		1,615,000	745,000	4,405,000	5,631,000				(1,700,000)					(100,000)
Area of property acquired															106,166
Acquisition, cash immediately defeased													10,100,000
Land purchased		58,119,000		58,119,000		41,313,000						200,000					7,600,000	300,000
Sale of Virginia Natural Gas office property	8,900,000
Net assets associated with sale of office property		477,768,000		477,768,000		357,748,000					5,200,000					9,100,000
Sale of Sentara Williamsburg office property							$ 15,400,000