Stock-based Compensation (Tables)

12 Months Ended

Dec. 31, 2011

Stock Based Compensation Tables [Abstract]

Schedule Of Share Based Compensation Stock Options Activity Table Text Block

					Weighted-
			Weighted-		Average
			Average		Remaining	Aggregate
			Exercise		Contractual	Intrinsic
		Shares	Price		Term	Value
Outstanding at January 1, 2011		5,488,880	$	56.89
Granted		534,168		91.70
Exercised		(1,173,875)		47.14
Cancelled or expired		(378,178)		81.02
Outstanding at December 31, 2011		4,470,995	$	61.56	5.5	$	87,889,000
Options vested and expected to vest at
	December 31, 2011	4,439,486	$	61.38	5.5	$	87,651,000
Options exercisable at December 31, 2011		2,395,763	$	57.20	3.4	$	56,181,000

Schedule Of Share Based Payment Award Stock Options Valuation Assumptions Table Text Block

	December 31,
	2011	2010	2009
Expected volatility	35.00%	35.00%	28.00%
Expected life	7.1years	7.90years	7.00years
Risk free interest rate	2.90%	3.60%	2.30%
Expected dividend yield	4.40%	4.90%	4.60%

Schedule Of Sharebased Compensation Restricted Stock And Restricted Stock Units Activity Table Text Block

			Weighted-Average
			Grant-Date
Unvested Shares		Shares	Fair Value
	Unvested at January 1, 2011	75,548	$	78.60
	Granted	11,362		91.70
	Vested	(24,384)		83.31
	Cancelled or expired	(1,298)		72.30
	Unvested at December 31, 2011	61,228		79.28

Schedule Of Sharebased Compensation Restricted Operating Partnership Units Activity Table [Text Block]

			Weighted-Average
			Grant-Date
Unvested Units		Units	Fair Value
	Unvested at January 1, 2011	720,457	$	56.78
	Granted	217,740		86.00
	Vested	(175,462)		58.47
	Cancelled or expired	(63,076)		58.50
	Unvested at December 31, 2011	699,659		65.29