Investments in Unconsolidated Real Estate Entities - Summary of Financial Information for Apartment LLCs (Parenthetical) (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Real Estate Properties [Line Items]
Real estate assets, net of accumulated depreciation	$ 842,925	$ 767,017
Investments in unconsolidated real estate entities	16,297	15,945
Apartment LLCs [Member]
Real Estate Properties [Line Items]
Real estate assets, net of accumulated depreciation	38,332	32,780
Investments in unconsolidated real estate entities	$ 16,297	$ 15,945

The cumulative amount of depreciation for real estate property held for investment purposes.

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(3))

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

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 1

-Article 7

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant