Stock-Based Compensation (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Stock-Based Compensation - (Details) [Abstract]
Number of shares reserved for issuance under the 2006 incentive plan	8,000,000
Shares reserved for issuance under the 2000 plan	17,000
Shares available to grant under the 2006 incentive plan	2,353,051
Percentage of eligible earnings designated to purchase common stock through the employee stock purchase plan (in hundredths)	10.00%
Discount rate to the average closing price at which employees may purchase stock (in hundredths)	5.00%
Stock based compensation expense under all plans	$ 31,700,000	$ 25,200,000	$ 27,500,000
Tax effect recognized in net income related to stock based compensation expense under all plans	11,100,000	8,800,000	9,600,000
Tax benefit from option exercises and vesting of restricted stock under all plans	12,700,000	7,300,000	2,000,000
Percentage of market value at which stock option are granted is typically not less than (in hundredths)	100.00%
Stock options typically vest over a minimum period of (in years)	3
Stock options typically vest over a maximum period of (in years)	5
Stock options typically expire after a minimum of (in years)	7
Stock options typically expire after a maximum of (in years)	10
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Compensation expense relating to outstanding options	12,200,000	9,000,000	9,100,000
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares Outstanding, beginning balance	3,933,440
Number of shares granted	755,000
Number of shares exercised	839,881
Number of shares canceled	25,897
Number of shares outstanding, ending balance	3,822,662	3,933,440
Summary of activities with respect to stock option plans, additional disclosures
Weighted average exercise price per share outstanding, beginning balance	$ 42.32
Weighted average exercise price per share granted	$ 74.06
Weighted average exercise price per share exercised	$ 33.62
Weighted average exercise price per share cancelled	$ 53.23
Weighted average exercise price per share outstanding, ending balance	$ 42.62	$ 42.32
Aggregate intrinsic value of options outstanding	139,243,760
Options Exercisable
Number of shares exercisable	2,238,712
Weighted average price per exercisable share	$ 50.44
Weighted average remaining contractual term, exercisable options (in years)	4.11
Aggregate intrinsic value, exercisable options	99,065,980
Weighted average fair value of options granted (per share)	$ 24.45	$ 17.00	$ 12.68
Weighted average assumptions used in calculating the weigthed average fair value of options granted
Risk-free interest rate (in hundredths)	1.91%	2.32%	1.78%
Average expected option life (in hundredths)	5.34	5.38	5.37
Expected Volatility (in hundredths)	35.27%	34.55%	32.24%
Expected dividend yield (in hundredths)	0.60%	0.72%	0.78%
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Total unrecognized compensation expense related to nonvested options granted	18,700,000
Weighted-average period over which unrecognized compensation costs on non-vested stock options are expected to be recognized (in years)	1.8
Intrinsic value of exercised options exercised	41,200,000	27,500,000	10,500,000
Cash received from option exercises under all plans	28,167,000	29,047,000	10,506,000
Restricted stock awards granted during the period	352,330	257,893
Minimum vesting period of restricted stock granted (in years)	1
Maximum vesting period of restricted stock granted (in years)	3
Weighted average grant date fair value per share	$ 74.66
Compensation expense related to outstanding shares of restricted stock	19,500,000	16,200,000	18,300,000
Summary of nonvested shares activity [Rollforward]
Non-vested shares outstanding, beginning of period	670,401
Nonvested shares granted	352,330
Nonvested shares vested	264,848	289,746
Nonvested shares forfeited	4,072
Nonvested shares outstanding, end of period	753,811	670,401
Summary of nonvested shares, additional disclosures
Weighted average fair value of nonvested shares, beginning of period	$ 52.64
Weighted average fair value of nonvested shares granted	$ 74.66
Weighted average fair value of shares vested	$ 78.12
Weighted average fair value of nonvested shares forfeited	$ 54.38
Weighted average fair value of nonvested shares, end of period	$ 61.15	$ 52.64
Total unrecognized compensation expense related to nonvested restricted stock granted to both employees and directors	20,300,000
Weighted-average period over which unrecognized compensation costs on non-vested restricted stock are expected to be recognized (in years)	2.2
Shares of restricted stock that vested during the period	264,848	289,746
Employee Stock Purchase Plan
Shares of stock purchased during the period by participants in the employee stock purchase plan	27,756	29,439	38,428
Amount paid for stock purchased during the period by participants in the employee stock purchase plan	$ 2,100,000	$ 1,700,000	$ 1,700,000
Exercise Price Range 1 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Minimum price of options outstanding, end of the period	$ 14.73
Maximum price of options outstanding, end of the period	$ 20.00
Options outstanding	281,938
Average exercise price of options outstanding	$ 19.05
Average remaining life of options outstanding (years)	0.9
Exercisable options	281,938
Average exercise price of exercisable options	$ 19.05
Exercise Price Range 2 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Minimum price of options outstanding, end of the period	$ 20.01
Maximum price of options outstanding, end of the period	$ 30.00
Options outstanding	222,096
Average exercise price of options outstanding	$ 23.48
Average remaining life of options outstanding (years)	2.1
Exercisable options	222,096
Average exercise price of exercisable options	$ 23.48
Exercise Price Range 3 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Minimum price of options outstanding, end of the period	$ 30.01
Maximum price of options outstanding, end of the period	$ 40.00
Options outstanding	186,322
Average exercise price of options outstanding	$ 32.12
Average remaining life of options outstanding (years)	0.3
Exercisable options	186,322
Average exercise price of exercisable options	$ 32.12
Exercise Price Range 4 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Minimum price of options outstanding, end of the period	$ 40.01
Maximum price of options outstanding, end of the period	$ 50.00
Options outstanding	657,166
Average exercise price of options outstanding	$ 42.77
Average remaining life of options outstanding (years)	4.7
Exercisable options	503,790
Average exercise price of exercisable options	$ 43.03
Exercise Price Range 5 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Minimum price of options outstanding, end of the period	$ 50.01
Maximum price of options outstanding, end of the period	$ 60.00
Options outstanding	1,691,307
Average exercise price of options outstanding	$ 53.47
Average remaining life of options outstanding (years)	6.5
Exercisable options	1,009,258
Average exercise price of exercisable options	$ 53.94
Exercise Price Range 6 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Minimum price of options outstanding, end of the period	$ 60.01
Maximum price of options outstanding, end of the period	$ 70.00
Options outstanding	135,333
Average exercise price of options outstanding	$ 67.69
Average remaining life of options outstanding (years)	9.3
Exercisable options	12,501
Average exercise price of exercisable options	$ 64.49
Exercise Price Range 7 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Minimum price of options outstanding, end of the period	$ 70.01
Maximum price of options outstanding, end of the period	$ 80.00
Options outstanding	570,100
Average exercise price of options outstanding	$ 73.59
Average remaining life of options outstanding (years)	9.1
Exercisable options	0.00
Average exercise price of exercisable options	$ 0.00
Exercise Price Range 8 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Minimum price of options outstanding, end of the period	$ 80.01
Maximum price of options outstanding, end of the period	$ 86.46
Options outstanding	78,400
Average exercise price of options outstanding	$ 84.19
Average remaining life of options outstanding (years)	9.2
Exercisable options	22,807
Average exercise price of exercisable options	$ 84.13