STOCK BENEFIT PLAN (Tables)

12 Months Ended

Dec. 31, 2012

Stock-based Compensation

Schedule of stock option, restricted stock and restricted stock unit awards granted to employees and non-employee directors under all stock benefit plans

	Employee Awards				Non-Employee Director Awards
Name of Plan	Stock Options Granted	Restricted Stock Granted	Restricted Stock Units Granted(a)	Total Granted	Stock Options Granted	Restricted Stock Granted	Total Granted	Available for Future Grant of Awards
1994 Plan	1,542,381	—	—	1,542,381	153,654	—	153,654	—
2000 Plan	2,101,220	350,702	—	2,451,922	163,760	2,700	166,460	—
2003 Plan	2,737,142	96,822	—	2,833,964	217,723	28,935	246,658	—
2008 Plan	1,354,837	290,131	—	1,644,968	134,146	36,313	170,459	—
2011 Plan	386,609	195,978	114,743	697,330	—	21,003	21,003	1,730,963

(a) Represents service-based awards of 19,119 and market-based awards of 95,624 at the maximum achievable level.

Schedule of weighted average assumptions used

Assumption	2012		2011		2010
Expected dividend yield	4.22	%	4.32	%	5.87	%
Expected volatility	26.53	%	25.98	%	19.31	%
Expected lives of the employee options	6.0 Years		6.0 Years		5.7 Years
Expected lives of the Director options	—		—		6.7 Years
Risk free interest rate	1.03	%	2.36	%	2.75	%

Schedule of performance hurdles used in measurement of performance

	2012 — 2014 Performance Goals
Market Requirements	Threshold	Target	High
Absolute TSR	7%	9%	11%
All REIT TSR Index	Absolute TSR is within 350 basis points below the index return	Absolute TSR is within 100 basis points below or above the index return	Absolute TSR is greater than 250 basis points above the index return
Apartment TSR Index	Absolute TSR is within 350 basis points below the index return	Absolute TSR is within 100 basis points below or above the index return	Absolute TSR is greater than 250 basis points above the index return

Unvested stock option

Stock-based Compensation

Summary of stock option activity

	Number of Options		Weighted Average Exercise Price Per Option
Unvested stock options at December 31, 2011	1,078,921		$	47.48
Granted	219,799		63.69
Vested	(462,249	)	48.51
Cancelled	(1,400	)	37.07
Unvested stock options at December 31, 2012	835,071		$	51.20

Stock options

Stock-based Compensation

Summary of stock option activity

	Number of Options		Weighted Average Exercise Price Per Option		Weighted Average Remaining Contractual Term in Years	Aggregate Intrinsic Value
Options outstanding at December 31, 2011	2,774,372		$	46.14
Granted	219,799		63.69
Exercised	(436,430	)	41.77
Cancelled	(1,400	)	37.07
Options outstanding at December 31, 2012	2,556,341		$	48.40	5.4	$	33,002
Options exercisable at December 31, 2012	1,721,270		$	47.04	4.4	$	24,563

Schedule of additional disclosure related to stock options

	2012		2011		2010
Stock-based compensation costs recognized	$	3,052	$	2,813	$	2,818
Fair value of options vested	2,717		2,562		2,457
Cash received from the exercise of options	18,228		23,843		14,090
Intrinsic value of options exercised	8,737		9,288		5,723
Grant date fair value of options granted to employees, per share	9.32		9.95		4.14
Grant date fair value of options granted to Directors, per share	—		—		4.33
Number of options granted to employees	219,799		166,810		352,454
Number of options granted to Directors	—		—		48,490

Restricted stock

Stock-based Compensation

Summary of restricted stock activity

	Number of Shares		Weighted Average Grant Date Fair Value Per Share
Restricted stock outstanding and unvested at December 31, 2011	289,448		$	50.29
Granted	119,604		63.62
Vested and issued	(107,546	)	50.39
Cancelled	(6,472	)	45.05
Restricted stock outstanding and unvested at December 31, 2012	295,034		$	55.77

Schedule of additional disclosure related to restricted stock awards

	2012		2011		2010
Stock-based compensation costs recognized	$	7,659	$	6,226	$	4,527
Fair value of restricted shares vested	6,707		5,246		3,447
Weighted average price of shares granted, per share	63.62		62.09		49.35
Number of restricted shares granted to employees	108,065		87,913		108,252
Number of restricted shares granted to Directors	11,539		9,464		12,760

Restricted Stock Units

Stock-based Compensation

Schedule of weighted average assumptions used

Assumption	2012
Baseline share value	$	55.87
Expected dividend yield	4.45		%
Expected volatility	31.24		%
Risk free interest rate	0.22		%
Estimated fair value per share of the market-based awards	$	51.40
Estimated fair value per share of the service-based awards	$	59.32

Summary of stock option activity

	Number of Awards		Weighted Average Grant Date Fair Value Per Share
Restricted stock units unvested at December 31, 2011	—		$	—
Granted (a)	114,743		53.39
Vested and issued (b)	(6,490	)	53.39
Forfeited	(3,245	)	53.39
Restricted stock units unvested at December 31, 2012	105,008		$	53.39

(a) Represents service-based awards of 19,119 and market-based awards of 95,624 at the maximum achievable level.

(b) Awards were issued in connection with the departure of an executive officer of the Company and were calculated in accordance with the 2012 Performance Plan.