Stock-based Compensation (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share Based Compensation Expense	$ 30,588,000	$ 28,853,000	$ 34,614,000
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	$ 60.96
Stock Options Granted Weighted Average Exercise Price	$ 82.86
Stock Options Exercised Weighted Average Exercise Price	$ 42.34
Stock Options Cancelled Weighted Average Exercise Price	$ 74.39
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price, End of Period	$ 67.16	$ 60.96
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number, Beginning Balance	4,514,341
Stock Options Granted Shares	47,720
Stock Options Exercised Shares	1,120,193
Stock Options Cancelled Shares	81,796
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number, Ending Balance	3,360,072	4,514,341
Options Vested And Expected To Vest Shares	3,353,953
Options Vested And Expected To Vest Weighted Average Exercise Price	$ 67.16
Options Excercisable Shares	1,970,247
Options Excercisable Weighted Average Exercise Price	$ 68.02
Options Exercisable Weighted Average Remaining Contractual Term	5 years 4 months 24 days
Options Outstanding Weighted Average Remaining Contractual Term	6 years 1 month 6 days
Options Vested And Expected To Vest Weighted Average Remaining Contractual Term	6 years 1 month 6 days
Options Outstanding Aggregate Intrinsic Value	56,414,000
Options Vested And Expected To Vest Aggregate Intrinsic Value	56,313,000
Options Excercisable Aggregate Intrinsic Value	32,914,000
Fair Value Assumptions Expected Volatility Rate	36.00%	35.00%	35.00%
Fair Value Assumptions Expected Life	5 years	7 years 1 month 6 days	7 years 10 months 24 days
Fair Value Assumptions Risk Free Interest Rate	1.05%	2.90%	3.60%
Fair Value Assumptions Risk Expected Dividend Yield	4.30%	4.40%	4.90%
Full Value Awards [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
Share Based Compensation Shares Available For Grant	5,136,000
Not Full Value Awards [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	12,000,000
Employee Stock Option [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share Based Compensation Expense	8,638,000	8,794,000	7,916,000
Out Performance Plan [Abstract]
Compensation Cost Not Yet Recognized	12,300,000
Compensation Cost Recognition Period	1 year 4 months
Award Vesting Period	4 years
Stock options expiration term	10 years
Share Based Compensation Employee Stock Purchase Plan Activity [Abstract]
Grant Date Fair Value Of Options	$ 17.50	$ 21.42	$ 16.96
Cash Received From Exercise Of Stock Options	9,546,000	23,736,000	25,338,000
Total Intrinsic Value Of Options Excercised	40,887,000	39,348,000	60,923,000
Restricted Stock Units RSU [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share Based Compensation Expense	1,604,000	1,814,000	1,432,000
Out Performance Plan [Abstract]
Fair Value Of Awards Granted	929,000	1,042,000	3,922,000
Compensation Cost Not Yet Recognized	2,823,000
Compensation Cost Recognition Period	1 year 7 months 6 days
Award Vesting Period	4 years
Dividends Paid On Nonvested Units	200,000	185,000	115,000
Fair Value Of Awards Vested	1,864,000	2,031,000	2,186,000
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	$ 79.28
Units Granted Weighted Average Grant Date Fair Value	$ 83.96
Awards Vested Weighted Average Grant Date Fair Value	$ 83.61
Units Cancelled Weighted Average Grant Date Fair Value	$ 72.97
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value, End of Period	$ 78.61	$ 79.28
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number, Beginning Balance	61,228
Restricted Stock Granted Shares	11,060
Units Vested	(22,297)
Forfeited Units	(1,971)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number, Ending Balance	48,020	61,228
Restricted Operating Partnership Units Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share Based Compensation Expense	17,520,000	17,505,000	20,204,000
Out Performance Plan [Abstract]
Fair Value Of Awards Granted	16,464,000	18,727,000	31,437,000
Compensation Cost Not Yet Recognized	16,853,000
Compensation Cost Recognition Period	1 year 6 months
Award Vesting Period	4 years
Dividends Paid On Nonvested Units	3,203,000	2,567,000	2,285,000
Fair Value Of Awards Vested	15,014,000	10,260,000	14,087,000
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	$ 65.29
Units Granted Weighted Average Grant Date Fair Value	$ 78.52
Awards Vested Weighted Average Grant Date Fair Value	$ 63.82
Units Cancelled Weighted Average Grant Date Fair Value	$ 75.93
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value, End of Period	$ 69.61	$ 65.29
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number, Beginning Balance	699,659
Restricted Stock Granted Shares	209,663
Units Vested	(235,245)
Forfeited Units	(33,407)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number, Ending Balance	640,670	699,659
Out Performance Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share Based Compensation Expense	2,826,000	740,000	5,062,000
Out Performance Plan [Abstract]
Out of performance plan notional amount	40,000,000
Award vesting in three years	33.00%
Award versting in four years	33.00%
Award vesting in five years	34.00%
Share Based Compensation By Share Based Payment Award Grant Date Fair Value Adjusted For Estimated Forfeitures	12,250,000
Compensation Cost Not Yet Recognized	9,435,000
Compensation Cost Recognition Period	2 years 2 months
Dividends Paid On Nonvested Units	$ 8,000	$ 32,000	$ 815,000
Out Performance Plan And Absolute Component [Member]
Out Performance Plan [Abstract]
Required Shareholder Return Per Year	7.00%
Required Shareholder Return Three Year	21.00%
Percentage Of Shareholder Return Under Which No Awards Will Be Earned	0.00%
Out Performance Plan And Relative Component [Member]
Out Performance Plan [Abstract]
Required Shareholder Return Under Relative Component	6.00%
Annual Incentive Program [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Minimum Comparable Funds From Operations To Prior Year	80.00%
Maximum Percentage Of Comparable Funds From Operations As Incentive Awards	1.25%