Summary of Investments in Real Estate (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013 Property	Dec. 31, 2012 Property
Real Estate Properties [Line Items]
Investments in real estate, Book Value	$ 1,061,974	$ 1,015,581
Less: Accumulated depreciation and amortization	(112,325)	(97,392)
Number of Properties	60	59
Investments in real estate, net, Book Value	949,649	918,189
Multi-family real estate properties
Real Estate Properties [Line Items]
Investments in real estate, Book Value	654,149	613,888
Number of Properties	35	34
Office real estate properties
Real Estate Properties [Line Items]
Investments in real estate, Book Value	276,119	271,847
Number of Properties	11	11
Retail real estate properties
Real Estate Properties [Line Items]
Investments in real estate, Book Value	83,197	82,081
Number of Properties	4	4
Parcels of land
Real Estate Properties [Line Items]
Investments in real estate, Book Value	$ 48,509	$ 47,765
Number of Properties	10	10

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

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- Definition

Amount of accumulated depreciation pertaining to real estate investments for entities with a substantial portion of business acquiring and holding investment real estate.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 970

-SubTopic 360

-Section S99

-Paragraph 1

-Subparagraph (SX 210.12-28.FN4)

-URI http://asc.fasb.org/extlink&oid=6590653&loc=d3e638233-123024

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 205

-SubTopic 10

-Section S99

-Paragraph 6

-Subparagraph (SX 210.5-04.(c) Schedule III)

-URI http://asc.fasb.org/extlink&oid=27047687&loc=d3e5864-122674

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 28

-Article 12

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph c

-Subparagraph Schedule III

-Article 5

+ Details

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- Definition

Amount of real estate investment property which may include the following: (1) land available-for-sale; (2) land available-for-development; (3) investments in building and building improvements; (4) tenant allowances; (5) developments in-process; (6) rental properties; and (7) other real estate investments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-03.1(d))

-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

+ Details

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- Definition

Amount of real estate investment property, net of accumulated depreciation, which may include the following: (1) land available-for-sale; (2) land available-for-development; (3) investments in building and building improvements; (4) tenant allowances; (5) developments in-process; (6) rental properties; and (7) other real estate investments.

+ References

+ Details

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