Acquisition, Development, Construction and Disposition Activity (Property Purchase) (Details) (USD $)	12 Months Ended						3 Months Ended				3 Months Ended				3 Months Ended				3 Months Ended				3 Months Ended				12 Months Ended	3 Months Ended					3 Months Ended		3 Months Ended		3 Months Ended		3 Months Ended				12 Months Ended		3 Months Ended				3 Months Ended		3 Months Ended		12 Months Ended
	Dec. 31, 2013 Units		Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2013 Lofts at Weston Lakeside [Member]		Nov. 19, 2013 Lofts at Weston Lakeside [Member] Units		Dec. 31, 2013 St. Mary's Square [Member]		Nov. 18, 2013 St. Mary's Square [Member] Units		Dec. 31, 2013 The Apartments at Blakeney [Member]		Oct. 10, 2013 The Apartments at Blakeney [Member] Units		Sep. 30, 2013 Rienzi at Turtle Creek [Member]		Sep. 27, 2013 Rienzi at Turtle Creek [Member] Units		Sep. 30, 2013 Doral West [Member]		Jul. 16, 2013 Doral West [Member] Units		Dec. 31, 2013 Acquisitions in Year 2013 [Member] Units	Sep. 30, 2012 The Park at Crossroads [Member]		Dec. 31, 2012 The Park at Crossroads [Member]	Aug. 28, 2012 The Park at Crossroads [Member] Units		Sep. 30, 2012 21-Forty Medical District [Member]	Jul. 23, 2012 21-Forty Medical District [Member] Units	Sep. 30, 2012 Southpoint Village [Member]	Jul. 17, 2012 Southpoint Village [Member] Units	Jun. 30, 2012 The Apartments at the Arboretum [Member]	May 23, 2012 The Apartments at the Arboretum [Member] Units	Jun. 30, 2012 Desmond's Tower [Member]		May 08, 2012 Desmond's Tower [Member] Units		Dec. 31, 2012 Acquisitions in Year 2012 [Member]	Dec. 31, 2013 Acquisitions in Year 2012 [Member] Units	Dec. 31, 2011 The Brixton [Member]		Oct. 17, 2011 The Brixton [Member] Units		Sep. 30, 2011 Dwell Vienna Metro [Member]	Aug. 09, 2011 Dwell Vienna Metro [Member] Units	Jun. 30, 2011 Waterstone at Wellington [Member]	Jun. 15, 2011 Waterstone at Wellington [Member] Units	Dec. 31, 2011 Acquisitions in Year 2011 [Member]	Dec. 31, 2012 Acquisitions in Year 2011 [Member] Units	May 08, 2012 Parking Lot [Member] Desmond's Tower [Member]
Business Acquisition [Line Items]
Apartment units owned	13,676								215	[1]			134	[1]			295	[1]			152	[1]			388	[1]	1,184				344	[1]		396		211		205			0	[2]		1,156			224	[3]		250		222		696
Acquisition cost	$ 80,200,000						$ 38,300,000	[1]			$ 27,325,000	[1]			$ 53,180,000	[1]			$ 48,900,000	[1]			$ 93,500,000	[1]			$ 261,205,000	$ 35,200,000	[1]				$ 53,350,000		$ 34,800,000		$ 39,250,000		$ 20,000,000	[2]			$ 182,600,000		$ 21,000,000	[3]			$ 82,600,000		$ 32,820,000		$ 136,420,000
Assumed loan	28,000,000	[4],[5],[6]	27,589,000	[4]	12,892,000	[4]											28,000,000													24,900,000	24,900,000														12,300,000		12,300,000
Mortgage loan assumed	28,000,000	[7]	27,589,000	[8]	12,892,000	[9]																									27,600,000	[4]															12,900,000	[4]
Parking lot	$ 3,313,000		$ 3,197,000		$ 2,319,000																																																		$ 17,300,000

[1] Purchase price includes assumed $24.9 million loan, with a fair value of $27.6 million

[2] In conjunction with our May 2012 acquisition of land for development of an apartment community, we acquired an operating commercial building. This amount represents the purchase price allocation of the commercial building component only. The purchase price allocation of $17.3 million, representing the parking lot to be used for development, is included in the "Consolidated Current Development" table within this Note.

[3] Purchase price includes assumed $12.3 million loan, with a fair value of $12.9 million

[4] Fair value was equal to principal amount of loan assumed in 2013 at the time of acquisition.

[5] Fair value amount of loan assumed in 2011 at the time of acquisition; actual principal amount of loan assumed was $12.3 million.

[6] Fair value amount of loan assumed in 2012 at the time of acquisition; actual principal amount of loan assumed was

[7] Principal balance on loan assumed in 2013 approximated fair value at time of acquisition.

[8] Fair value amount of loan assumed in 2012 at time of acquisition. The principal balance at time of acquisition was $24.9 million. Fair value was determined based on an interest rate of 3.1%.

[9] Fair value amount of loan assumed in 2011 at time of acquisition. The principal balance at time of acquisition was $12.3 million. Fair value was determined based on an interest rate of 4.5%.