In a business combination in which the amount of net identifiable assets acquired and liabilities assumed exceeds the aggregate consideration transferred or to be transferred (as defined), this element represents the amount of gain recognized by the entity.

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Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer.

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Amount of liabilities assumed at the acquisition date.

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Amount of long-term debt due after one year or the normal operating cycle, if longer, assumed at the acquisition date.

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The amount of property, plant, and equipment recognized as of the acquisition date.

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The amount of the limited partners' ownership interests.

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The number of limited partner units issued.

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Stated maturity date of the mortgage loan receivable on real estate, in CCYY-MM-DD format.

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The stated interest rate on the mortgage loan receivable or the weighted average interest rate on a group of loans.

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The number of real estate properties owned as of the balance sheet date.

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Investments in Real Estate - Additional Information (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	0 Months Ended		12 Months Ended	0 Months Ended
	Sep. 15, 2014	Aug. 28, 2014	Dec. 31, 2014	Nov. 22, 2013	Sep. 19, 2013	Dec. 30, 2014	Dec. 16, 2014	Dec. 08, 2014	Nov. 24, 2014	Sep. 05, 2014	Jun. 04, 2014	May 07, 2014	Mar. 31, 2014	Feb. 28, 2014	Jan. 31, 2014
Real Estate Properties [Line Items]
Number of multifamily property owned			30us-gaap_NumberOfRealEstateProperties
Loans payable on real estate			186,512
Fair value of properties acquired			496,000
Investments in real estate			190,761
Walnut Hill
Real Estate Properties [Line Items]
Purchased price of a property		27,900
Effective interest rate	3.40%		3.40%
Maturity date			Oct. 01, 2021
Noncontrolling Interest \| Walnut Hill
Real Estate Properties [Line Items]
Number of limited units issued		137,361
Limited units issued value		1,377
The Crossings at Ridgewood Apartments
Real Estate Properties [Line Items]
Purchased price of a property				23,000
Berkshire Square Apartments
Real Estate Properties [Line Items]
Purchased price of a property					13,250
Iron Rock Ranch
Real Estate Properties [Line Items]
Purchased price of a property						35,250
Iron Rock Ranch \| Noncontrolling Interest
Real Estate Properties [Line Items]
Number of limited units issued						918,098
Limited units issued value						8,550
Stonebridge At The Ranch
Real Estate Properties [Line Items]
Purchased price of a property							31,580
Prospect Park Brookside Jamestown Meadows And Oxmoor
Real Estate Properties [Line Items]
Number of multifamily property owned								5
Purchased price of a property								162,350
Bennington Pond
Real Estate Properties [Line Items]
Purchased price of a property									17,500
Bennington Pond \| Noncontrolling Interest
Real Estate Properties [Line Items]
Number of limited units issued									4,929
Limited units issued value									48
Stonebridge Crossing
Real Estate Properties [Line Items]
Purchased price of a property	29,800
Lenoxplace At Garner Station
Real Estate Properties [Line Items]
Purchased price of a property										24,250
Arbors at the Reservoir
Real Estate Properties [Line Items]
Purchased price of a property											20,250
Carrington
Real Estate Properties [Line Items]
Purchased price of a property												21,500
Carrington \| Noncontrolling Interest
Real Estate Properties [Line Items]
Number of limited units issued												222,062
Limited units issued value												1,986
King's Landing
Real Estate Properties [Line Items]
Purchased price of a property													32,700
Loans payable on real estate													21,200
Effective interest rate													4.00%
OKC Portfolio
Real Estate Properties [Line Items]
Number of multifamily property owned														5
Purchased price of a property														65,000
Loans payable on real estate														45,763
Effective interest rate														5.60%
Maturity date														Apr. 01, 2016
Fair value of properties acquired														70,431
Investments in real estate														48,312
Gain (loss) on assets														2,882
Reserve at Eagle Ridge
Real Estate Properties [Line Items]
Purchased price of a property															$ 29,000