Subsequent Events (Details) (USD $)	12 Months Ended	1 Months Ended
Dec. 31, 2012 home	Jan. 31, 2013 Subsequent Events Avalon Yerba Buena Fund I home	Jan. 31, 2013 Subsequent Events Avalon Rothbury Fund II home
Subsequent Events
Number of communities sold	4	1	1
Number of apartment homes sold		160	205
Proceeds from sale of real estate		$ 103,000,000	$ 39,600,000

Cash received for the sale of real estate that is not part of an investing activity during the current period.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 12

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3179-108585

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 24

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Name:	us-gaap_ProceedsFromSaleOfRealEstate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration