Stock-based Compensation (Details) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended							12 Months Ended
	Dec. 31, 2011 Y	Dec. 31, 2010 Y	Dec. 31, 2009 Y	Dec. 31, 2011 Full Value Awards [Member]	Dec. 31, 2011 Not Full Value Awards [Member]	Mar. 31, 2008 Out Performance Plan 2008 [Member]	Apr. 30, 2006 Out Performance Plan 2006 [Member]	Dec. 31, 2011 Out Performance Plan 2008 And 2006 [Member]	Dec. 31, 2010 Out Performance Plan 2008 And 2006 [Member]	Dec. 31, 2009 Out Performance Plan 2008 And 2006 [Member]	Dec. 31, 2011 Employee Stock Option [Member] Y	Dec. 31, 2010 Employee Stock Option [Member]	Dec. 31, 2009 Employee Stock Option [Member]	Dec. 31, 2011 Restricted Stock Units RSU [Member] Y	Dec. 31, 2010 Restricted Stock Units RSU [Member]	Dec. 31, 2009 Restricted Stock Units RSU [Member]	Dec. 31, 2011 Restricted Operating Partnership Units Plan [Member] Y	Dec. 31, 2010 Restricted Operating Partnership Units Plan [Member]	Dec. 31, 2009 Restricted Operating Partnership Units Plan [Member]	Dec. 31, 2010 Restricted Operating Partnership And 2006 Out Performance Plan Combined [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share Based Compensation Arrangement By Share Based Payment Award Number Of Shares Authorized				6,000,000	12,000,000
Share Based Compensation Shares Available For Grant				5,582,000
Share Based Compensation Expense	$ 28,853	$ 34,614	$ 59,814					$ 740	$ 5,062	$ 23,493	$ 8,794	$ 7,916	$ 25,911	$ 1,814	$ 1,432	$ 2,063	$ 17,505	$ 20,204	$ 8,347
Unamortized Portion Of Awards Expensed	0	0	32,588							13,722			18,866
Additional Expense From Acceleration Of Vesting																				2,800
Out Performance Plan [Abstract]
Share Based Compensation Amount Authorized						75,000	100,000
Fair Value Of Awards Granted						21,600	46,141							1,042	3,922	496	18,727	31,437	10,691
Award Amortization Period						5 years	5 years
Compensation Cost Not Yet Recognized								510			20,398			3,567			18,903
Compensation Cost Recognition Period											1.8			1.9			1.5
Award Vesting Period											4 years			4 years			4 years
Stock options expiration term											10 years
Dividends Paid On Nonvested Units								32	815	1,935				185	115	161	2,567	2,285	1,583
Fair Value Of Awards Vested														2,031	2,186	3,272	10,260	14,087	4,020
Share Based Compensation Employee Stock Purchase Plan Activity [Abstract]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price, Beginning of Period	$ 56.89
Stock Options Granted Weighted Average Exercise Price	$ 91.70
Stock Options Exercised Weighted Average Exercise Price	$ 47.14
Stock Options Cancelled Weighted Average Exercise Price	$ 81.02
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price, End of Period	$ 61.56	$ 56.89
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number, Beginning Balance	5,488,880
Stock Options Granted Shares	534,168
Stock Options Exercised Shares	1,173,875
Stock Options Cancelled Shares	378,178
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number, Ending Balance	4,470,995	5,488,880
Options Vested And Expected To Vest Shares	4,439,486
Options Vested And Expected To Vest Weighted Average Exercise Price	$ 61.38
Options Excercisable Shares	2,395,763
Options Excercisable Weighted Average Exercise Price	$ 57.20
Options Exercisable Weighted Average Remaining Contractual Term	3.4
Options Outstanding Weighted Average Remaining Contractual Term	5.5
Options Vested And Expected To Vest Weighted Average Remaining Contractual Term	5.5
Options Outstanding Aggregate Intrinsic Value	87,889
Options Vested And Expected To Vest Aggregate Intrinsic Value	87,651
Options Excercisable Aggregate Intrinsic Value	56,181
Fair Value Assumptions Expected Volatility Rate	35.00%	35.00%	28.00%
Fair Value Assumptions Expected Life	7.1	7.90	7.00
Fair Value Assumptions Risk Free Interest Rate	2.90%	3.60%	2.30%
Fair Value Assumptions Risk Expected Dividend Yield	4.40%	4.90%	4.60%
Grant Date Fair Value Of Options											$ 21.42	$ 16.96	$ 5.67
Cash Received From Exercise Of Stock Options											23,736	25,338	1,749
Total Intrinsic Value Of Options Excercised											$ 39,348	$ 60,923	$ 62,139
Share Based Compensation Equity Instruments Other Than Options Plan Activity [Abstract]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value, Beginning of Period														$ 78.60			$ 56.78
Units Granted Weighted Average Grant Date Fair Value														$ 91.70			$ 86.00
Awards Vested Weighted Average Grant Date Fair Value														$ 83.31			$ 58.47
Units Cancelled Weighted Average Grant Date Fair Value														$ 72.30			$ 58.50
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value, End of Period														$ 79.28	$ 78.60		$ 65.29	$ 56.78
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number, Beginning Balance														75,548			720,457
Restricted Stock Granted Shares														11,362			217,740
Units Vested														24,384			175,462
Forfeited Units														1,298			63,076
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number, Ending Balance														61,228	75,548		699,659	720,457