Reportable Segments (Tables)

12 Months Ended

Dec. 31, 2011

Reportable Segments (Tables) [Abstracts]

Reportable Segments Schedule

	Year Ended December 31, 2011
	Northeast		Northwest		Southeast		Southwest		Other (3)			Total
Rental income:
Same store (1)	$	584,405	$	344,615	$	356,936	$	426,472	$	—		$	1,712,428
Non-same store/other (2) (3)	157,907		42,633		16,487		45,489		5,493			268,009
Total rental income	742,312		387,248		373,423		471,961		5,493			1,980,437
Operating expenses:
Same store (1)	211,494		120,920		140,145		145,153		—			617,712
Non-same store/other (2) (3)	56,591		16,021		5,974		17,619		7,366			103,571
Total operating expenses	268,085		136,941		146,119		162,772		7,366			721,283
NOI:
Same store (1)	372,911		223,695		216,791		281,319		—			1,094,716
Non-same store/other (2) (3)	101,316		26,612		10,513		27,870		(1,873		)	164,438
Total NOI	$	474,227	$	250,307	$	227,304	$	309,189	$	(1,873	)	$	1,259,154
Total assets	$	6,539,328	$	2,885,791	$	2,506,330	$	3,385,517	$	1,342,337		$	16,659,303

(1) Same store primarily includes all properties acquired or completed and stabilized prior to January 1, 2010, less properties subsequently sold, which represented 101,312 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.

	Year Ended December 31, 2010
	Northeast		Northwest		Southeast		Southwest		Other (3)			Total
Rental income:
Same store (1)	$	553,561	$	322,427	$	342,080	$	412,414	$	—		$	1,630,482
Non-same store/other (2) (3)	95,493		18,825		9,009		13,587		(3,604		)	133,310
Total rental income	649,054		341,252		351,089		426,001		(3,604		)	1,763,792
Operating expenses:
Same store (1)	207,131		119,797		139,550		147,732		—			614,210
Non-same store/other (2) (3)	48,119		8,300		3,729		7,198		12,230			79,576
Total operating expenses	255,250		128,097		143,279		154,930		12,230			693,786
NOI:
Same store (1)	346,430		202,630		202,530		264,682		—			1,016,272
Non-same store/other (2) (3)	47,374		10,525		5,280		6,389		(15,834		)	53,734
Total NOI	$	393,804	$	213,155	$	207,810	$	271,071	$	(15,834	)	$	1,070,006
Total assets	$	6,158,908	$	2,630,850	$	2,495,748	$	3,140,153	$	1,758,535		$	16,184,194

(1) Same store primarily includes all properties acquired or completed and stabilized prior to January 1, 2010, less properties subsequently sold, which represented 101,312 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 $0.6 million and other corporate operations.

	Year Ended December 31, 2009
	Northeast		Northwest		Southeast		Southwest		Other (3)			Total
Rental income:
Same store (1)	$	566,518	$	357,502	$	383,239	$	423,076	$	—		$	1,730,335
Non-same store/other (2) (3)	23,195		2,010		4,268		16,985		69,364			115,822
Properties sold in 2011 (4)	—		—		—		—		(216,279		)	(216,279		)
Total rental income	589,713		359,512		387,507		440,061		(146,915		)	1,629,878
Operating expenses:
Same store (1)	211,352		129,696		158,977		148,483		—			648,508
Non-same store/other (2) (3)	12,798		1,851		1,727		9,418		68,692			94,486
Properties sold in 2011 (4)	—		—		—		—		(111,589		)	(111,589		)
Total operating expenses	224,150		131,547		160,704		157,901		(42,897		)	631,405
NOI:
Same store (1)	355,166		227,806		224,262		274,593		—			1,081,827
Non-same store/other (2) (3)	10,397		159		2,541		7,567		672			21,336
Properties sold in 2011 (4)	—		—		—		—		(104,690		)	(104,690		)
Total NOI	$	365,563	$	227,965	$	226,803	$	282,160	$	(104,018	)	$	998,473

(1) Same store primarily includes all properties acquired or completed and stabilized prior to January 1, 2009, less properties subsequently sold, which represented 112,042 apartment units.

(2) Non-same store primarily includes properties acquired after January 1, 2009, plus any properties in lease-up and not stabilized as of January 1, 2009.

(3) Other includes development, condominium conversion overhead of $1.4 million and other corporate operations.

(4) Reflects discontinued operations for properties sold during 2011.

Reconciliation of NOI

	Year Ended December 31,
	2011			2010			2009
Rental income	$	1,980,437		$	1,763,792		$	1,629,878
Property and maintenance expense	(416,723		)	(402,078		)	(369,731		)
Real estate taxes and insurance expense	(222,427		)	(211,621		)	(190,374		)
Property management expense	(82,133		)	(80,087		)	(71,300		)
Total operating expenses	(721,283		)	(693,786		)	(631,405		)
Net operating income	$	1,259,154		$	1,070,006		$	998,473