Reportable Segments (Tables)

9 Months Ended

Sep. 30, 2011

Reportable Segments [Abstract]

Reportable Segments Schedule

	Nine Months Ended September 30, 2011
	Northeast		Northwest		Southeast		Southwest		Other (3)			Total
Rental income:
Same store (1)	$	440,444	$	255,986	$	266,938	$	320,840	$	—		$	1,284,208
Non-same store/other (2) (3)		113,008		28,544		11,283		30,069		3,286			186,190
Total rental income		553,452		284,530		278,221		350,909		3,286			1,470,398
Operating expenses:
Same store (1)		160,900		91,053		106,223		109,768		—			467,944
Non-same store/other (2) (3)		43,631		10,911		4,162		12,257		6,308			77,269
Total operating expenses		204,531		101,964		110,385		122,025		6,308			545,213
NOI:
Same store (1)		279,544		164,933		160,715		211,072		—			816,264
Non-same store/other (2) (3)		69,377		17,633		7,121		17,812		(3,022	)		108,921
Total NOI	$	348,921	$	182,566	$	167,836	$	228,884	$	(3,022	)	$	925,185
Total assets	$	6,313,643	$	2,656,529	$	2,514,066	$	3,230,549	$	1,042,030		$	15,756,817

(1) Same store primarily includes all properties acquired or completed and stabilized prior to January 1, 2010, less properties subsequently sold, which represented 102,129 apartment units.

(2) Non-same store primarily includes properties acquired after January 1, 2010, plus any properties in lease-up and not stabilized as of January 1, 2010.

(3) Other includes development, condominium conversion overhead of $0.3 million and other corporate operations.

	Nine Months Ended September 30, 2010
	Northeast		Northwest		Southeast		Southwest		Other (3)			Total
Rental income:
Same store (1)	$	417,347	$	240,767	$	256,307	$	310,950	$	—		$	1,225,371
Non-same store/other (2) (3)		64,743		10,698		6,429		7,629		(3,493	)		86,006
Total rental income		482,090		251,465		262,736		318,579		(3,493	)		1,311,377
Operating expenses:
Same store (1)		158,351		91,045		106,245		113,510		—			469,151
Non-same store/other (2) (3)		34,241		4,531		2,728		3,490		9,852			54,842
Total operating expenses		192,592		95,576		108,973		117,000		9,852			523,993
NOI:
Same store (1)		258,996		149,722		150,062		197,440		—			756,220
Non-same store/other (2) (3)		30,502		6,167		3,701		4,139		(13,345	)		31,164
Total NOI	$	289,498	$	155,889	$	153,763	$	201,579	$	(13,345	)	$	787,384

(1) Same store primarily includes all properties acquired or completed and stabilized prior to January 1, 2010, less properties subsequently sold, which represented 102,129 apartment units.

(2) Non-same store primarily includes properties acquired after January 1, 2010, plus any properties in lease-up and not stabilized as of January 1, 2010.

(3) Other includes development, condominium conversion overhead of $0.4 million and other corporate operations.

	Quarter Ended September 30, 2011
	Northeast		Northwest		Southeast		Southwest		Other (3)		Total
Rental income:
Same store (1)	$	163,887	$	91,663	$	90,979	$	110,779	$	—	$	457,308
Non-same store/other (2) (3)		27,889		6,657		3,773		10,862		2,541		51,722
Total rental income		191,776		98,320		94,752		121,641		2,541		509,030
Operating expenses:
Same store (1)		59,736		32,455		35,861		38,160		—		166,212
Non-same store/other (2) (3)		9,163		2,645		1,250		4,351		1,338		18,747
Total operating expenses		68,899		35,100		37,111		42,511		1,338		184,959
NOI:
Same store (1)		104,151		59,208		55,118		72,619		—		291,096
Non-same store/other (2) (3)		18,726		4,012		2,523		6,511		1,203		32,975
Total NOI	$	122,877	$	63,220	$	57,641	$	79,130	$	1,203	$	324,071

(1) Same store primarily includes all properties acquired or completed and stabilized prior to July 1, 2010, less properties subsequently sold, which represented 104,922 apartment units.

(2) Non-same store primarily includes properties acquired after July 1, 2010, plus any properties in lease-up and not stabilized as of July 1, 2010.

(3) Other includes development, condominium conversion overhead of $0.1 million and other corporate operations.

	Quarter Ended September 30, 2010
	Northeast		Northwest		Southeast		Southwest		Other (3)			Total
Rental income:
Same store (1)	$	155,119	$	84,969	$	86,963	$	106,457	$	—		$	433,508
Non-same store/other (2) (3)		12,963		2,158		2,002		2,537		(1,336	)		18,324
Total rental income		168,082		87,127		88,965		108,994		(1,336	)		451,832
Operating expenses:
Same store (1)		58,184		32,805		36,219		39,173		—			166,381
Non-same store/other (2) (3)		10,321		855		565		1,114		242			13,097
Total operating expenses		68,505		33,660		36,784		40,287		242			179,478
NOI:
Same store (1)		96,935		52,164		50,744		67,284		—			267,127
Non-same store/other (2) (3)		2,642		1,303		1,437		1,423		(1,578	)		5,227
Total NOI	$	99,577	$	53,467	$	52,181	$	68,707	$	(1,578	)	$	272,354

(1) Same store primarily includes all properties acquired or completed and stabilized prior to July 1, 2010, less properties subsequently sold, which represented 104,922 apartment units.

(2) Non-same store primarily includes properties acquired after July 1, 2010, plus any properties in lease-up and not stabilized as of July 1, 2010.

(3) Other includes development, condominium conversion overhead of $0.1 million and other corporate operations.

Note: Markets included in the above geographic segments are as follows:

(a) Northeast – New England (excluding Boston), Boston, New York Metro, DC Northern Virginia and Suburban Maryland.

(b) Northwest – Denver, Portland, San Francisco Bay Area and Seattle/Tacoma.

(c) Southeast – Atlanta, Jacksonville, Orlando and South Florida.

(d) Southwest – Inland Empire, Los Angeles, Orange County, Phoenix and San Diego.

Reconciliation of NOI

	Nine Months Ended September 30,						Quarter Ended September 30,
	2011			2010			2011			2010
Rental income	$	1,470,398		$	1,311,377		$	509,030		$	451,832
Property and maintenance expense		(314,768	)		(303,916	)		(106,635	)		(104,259	)
Real estate taxes and insurance expense		(168,056	)		(160,307	)		(59,083	)		(56,205	)
Property management expense		(62,389	)		(59,770	)		(19,241	)		(19,014	)
Total operating expenses		(545,213	)		(523,993	)		(184,959	)		(179,478	)
Net operating income	$	925,185		$	787,384		$	324,071		$	272,354