v2.4.0.6
Stock-Based Compensation (Details) (USD $)
 3 Months Ended 9 Months Ended
Sep. 30, 2012
Sep. 30, 2011
Sep. 30, 2012
Sep. 30, 2011
Stock based compensation by job function [Line Items]        
Compensation expense related to the company's stock-based compensation plans $ 45,900,000 $ 41,600,000 $ 101,300,000 $ 95,000,000
Common Shares Available for Grant 3,300,000   3,300,000  
Stock-based compensation expense related to stock options, SAR and ESPP grants 16,500,000 13,500,000 37,800,000 33,400,000
Summary Information By Grant Price Range For Stock Options And SARs Outstanding And Exercisable At End Of Period [Line Items]        
Aggregate Intrinsic Value For Outstanding Options and SARs 231,100,000 91,000,000 231,100,000 91,000,000
Weighted Average Remaining Contractual Life for Stock Options/SARs Outstanding     4.1 3.9
Aggregate Intrinsic Value For Exercisable Units 182,700,000 90,900,000 182,700,000 90,900,000
Weighted Average Remaining Contractual Life for Exercisable Options and SARs (in years)     2.7 2.6
Unrecognized compensation expense related to non-vested stock option and SAR grants 100,700,000   100,700,000  
Weighted average period over which unrecognized compensation expense will be recognized (in years)     2.8  
Stock Options/SARs and Employee Stock Purchase Plan (ESPP) Disclosures [Line Items]        
Stock Options/SARs Exercisable at September 30 (in shares) 4,315 5,382 4,315 5,382
Stock Options/SARs Exercisable at September 30 (price per share) $ 69.87 $ 59.25 $ 69.87 $ 59.25
Stock options/SARs vested or expected to vest (in shares) 7,184 8,387 7,184 8,387
Weighted average grant price for stock options/SARs vested or expected to vest (per share) $ 80.57 $ 69.29 $ 80.57 $ 69.29
Share Based Compensation Arrangement By Share Based Payment Award Stock Option/SAR [Abstract]        
Weighted Average Remaining Contractual Life for Stock Options/SARs Vested or Expected to Vest     4.0 3.8
Intrinsic value of stock options/SARs exercised during the period     110,800,000 69,300,000
Intrinsic value of stock options/SARs vested or expected to vest 227,300,000 91,000,000 227,300,000 91,000,000
Restricted Stock and Restricted Stock Unit [Roll Forward]        
Employee Service Share Based Compensation Unrecognized Compensation Costs On Nonvested Restricted Stock Awards 151,800,000   151,800,000  
Employee Service Share Based Compensation Unrecognized Compensation Costs On Nonvested Restricted Stock Awards Weighted Average Period Of Recognition     2.5  
Weighted Average Grant Price Restricted Stock and Restricted Stock Units Rollforward [Abstract]        
Outstanding at January 1 - Price (per share)     82.93 79.13
Granted - Price (per share)     112.13 90.93
Released - Price (per share)     72.97 65.77
Forfeited - Price (per share) $ 88.36 $ 82.51 $ 88.36 $ 82.51
Outstanding at September 30 - Price (per share) 90.91 82.75 90.91 82.75
Share Based Compensation Arrangement By Restricted Stock And Restricted Stock Units Compensation Cost 23,100,000 28,100,000 57,200,000 61,600,000
Intrinsic value of restricted stock and restricted stock units released during the year (in millions) $ 110.7 $ 40.0 $ 110.7 $ 40.0
Aggregate Intrinsic Value Of Restricted Stock And Restricted Stock Units Outstanding 438,600,000 306,400,000 438,600,000 306,400,000
Performance Units and Performance Stock [Member]
        
Weighted Average Fair Value And Valuation Assumptions Used To Value Stock Options/SARs, ESPP, and Performance Units/Stock Stock Based Compensation [Abstract]        
Weighted Average Fair Value of Grants     $ 134.09  
Expected Volatility (in hundredths)     3639.00%  
Risk-Free Interest Rate (in hundredths)     0.39%  
Dividend Yield (in hundredths)     0.06%  
Performance Units and Performance Stock [Abstract]        
Performance Units Granted 54,526   54,526  
Performance Stock Granted 16,752   16,752  
Minimum Performance Units and Stock Allowed to be Outstanding 0   0  
Maximum Performance Units And Stock Allowed To Be Outstanding 142,556   142,556  
Share Based Compensation Arrangement By Performance Units and Stock Compensation Cost 6,300,000   6,300,000  
Employee Service Share Based Compensation Unrecognized Compensation Costs On Nonvested Performance Units and Stock Awards 3,100,000   3,100,000  
Employee Service Share Based Compensation Unrecognized Compensation Costs On Nonvested Performance Units and Stock Awards Weighted Average Period Of Recognition 3.3   3.3  
Term of Zero-Coupon Risk-Free Interest Rate (in years) Derived from the Treasury Constant Maturities Yield Curve 3.26   3.26  
Stock Options And Sars [Member]
        
Weighted Average Fair Value And Valuation Assumptions Used To Value Stock Options/SARs, ESPP, and Performance Units/Stock Stock Based Compensation [Abstract]        
Weighted Average Fair Value of Grants     $ 37.94 $ 29.87
Expected Volatility (in hundredths)     39.68% 40.92%
Risk-Free Interest Rate (in hundredths)     0.45% 0.58%
Dividend Yield (in hundredths)     0.60% 0.70%
Expected Life (in years)     5.6 5.6
Stock Options and SARs Rollforward [Abstract]        
Outstanding at January 1     8,374 8,445
Granted     1,223 1,470
Exercised (1)     (2,044) (1,150)
Forfeited     (124) (133)
Outstanding at September 30 7,429 8,632 7,429 8,632
Share Based Compensation Arrangement By Share Based Payment Award Stock Option/SAR [Abstract]        
Outstanding at January 1 - Price per Share     $ 70.01 $ 64.49
Granted - Price Per Share     $ 111.91 $ 85.25
Exercised - Price Per Share     $ 53.52 $ 48.41
Forfeited - Price per Share     $ 89.95 $ 87.75
Outstanding at September 30 - Price per Share $ 81.11 $ 69.80 $ 81.11 $ 69.80
Espp [Member]
        
Weighted Average Fair Value And Valuation Assumptions Used To Value Stock Options/SARs, ESPP, and Performance Units/Stock Stock Based Compensation [Abstract]        
Weighted Average Fair Value of Grants     $ 25.17 $ 22.35
Expected Volatility (in hundredths)     41.04% 29.68%
Risk-Free Interest Rate (in hundredths)     0.11% 0.18%
Dividend Yield (in hundredths)     0.60% 0.70%
Expected Life (in years)     0.5 0.5
Restricted Stock And Restricted Stock Units [Member]
        
Restricted Stock and Restricted Stock Unit [Roll Forward]        
Outstanding at January 1     4,240 4,009
Granted     757 917
Released (1)     (977) (410)
Forfeited     (106) (202)
Outstanding at September 30 (2) 3,914 4,314 3,914 4,314
Lease And Well [Member]
        
Stock based compensation by job function [Line Items]        
Compensation expense related to the company's stock-based compensation plans 9,900,000 9,500,000 26,400,000 24,400,000
Gathering And Processing Costs [Member]
        
Stock based compensation by job function [Line Items]        
Compensation expense related to the company's stock-based compensation plans 300,000 200,000 800,000 600,000
Exploration Costs [Member]
        
Stock based compensation by job function [Line Items]        
Compensation expense related to the company's stock-based compensation plans 7,400,000 7,800,000 20,300,000 19,400,000
General And Administrative [Member]
        
Stock based compensation by job function [Line Items]        
Compensation expense related to the company's stock-based compensation plans $ 28,300,000 $ 24,100,000 $ 53,800,000 $ 50,600,000