The cash outflow from the acquisition of real estate intended to generate income for the owner; excludes land acquired for use by the owner.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 17

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 13

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3213-108585

Name:	us-gaap_PaymentsToAcquireLand
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Property Acquisitions, Discontinued Operations, And Assets Held For Sale (Narrative) (Details) (USD $) In Millions, unless otherwise specified	1 Months Ended	3 Months Ended		9 Months Ended
	Aug. 31, 2011 A	Sep. 30, 2011	Dec. 31, 2010	Sep. 30, 2011
Property Acquisitions, Discontinued Operations, And Assets Held For Sale [Abstract]
Acres of land acquired	30.1
Acquisitions of land	$ 40.1
Number of operating properties sold			2
Number of apartment homes in operating properties sold			1,066
Number of assets classified as held for sale		0		0