Quarterly report pursuant to Section 13 or 15(d)

Carrying Value of Outstanding Debt (Detail)

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Carrying Value of Outstanding Debt (Detail)
CAD in Millions
9 Months Ended
Sep. 30, 2017
USD ($)
May 15, 2017
USD ($)
May 15, 2017
CAD
May 11, 2017
USD ($)
Dec. 31, 2016
USD ($)
Debt Instrument [Line Items]          
Debt Instrument, Face Amount $ 18,897,000,000        
Debt instrument, stated interest rate 8.375%        
Total debt $ 18,910,000,000       $ 16,075,000,000
Less current maturities (4,555,000,000)       (3,681,000,000)
Long-Term Debt 14,355,000,000       12,394,000,000
Commercial Paper          
Debt Instrument [Line Items]          
Debt Instrument, Face Amount $ 4,120,000,000        
Maturity - Minimum Date Mar. 31, 2017        
Maturity - Maximum Date Dec. 31, 2018        
Total debt $ 4,120,000,000       3,250,000,000
Senior notes | 1.125% senior notes          
Debt Instrument [Line Items]          
Debt Instrument, Face Amount $ 375,000,000        
Maturity - Maximum Date Dec. 31, 2017        
Debt instrument, stated interest rate 1.125%        
Total debt $ 375,000,000       374,000,000
Senior notes | 5.50% stated rate          
Debt Instrument [Line Items]          
Debt Instrument, Face Amount $ 750,000,000        
Maturity - Maximum Date Dec. 31, 2018        
Debt instrument, stated interest rate 5.50%        
Total debt $ 755,000,000       769,000,000
Senior notes | 5.125% stated rate          
Debt Instrument [Line Items]          
Debt Instrument, Face Amount $ 1,000,000,000        
Maturity - Maximum Date Dec. 31, 2019        
Debt instrument, stated interest rate 5.125%        
Total debt $ 1,027,000,000       1,043,000,000
Senior notes | 3.125% stated rate          
Debt Instrument [Line Items]          
Debt Instrument, Face Amount $ 1,500,000,000        
Maturity - Maximum Date Dec. 31, 2021        
Debt instrument, stated interest rate 3.125%        
Total debt $ 1,567,000,000       1,584,000,000
Senior notes | 2.40% senior notes          
Debt Instrument [Line Items]          
Debt Instrument, Face Amount $ 500,000,000        
Maturity - Maximum Date Dec. 31, 2026        
Debt instrument, stated interest rate 2.40%        
Total debt $ 497,000,000       497,000,000
Senior notes | 2.45% senior notes          
Debt Instrument [Line Items]          
Debt Instrument, Face Amount $ 1,000,000,000        
Maturity - Maximum Date Dec. 31, 2022        
Debt instrument, stated interest rate 2.45%        
Total debt $ 989,000,000       986,000,000
Senior notes | 2.35% senior notes          
Debt Instrument [Line Items]          
Debt Instrument, Face Amount $ 600,000,000     $ 600,000,000  
Maturity - Maximum Date Dec. 31, 2022        
Debt instrument, stated interest rate 2.35%     2.35%  
Total debt $ 596,000,000       0
Senior notes | 6.20% stated rate          
Debt Instrument [Line Items]          
Debt Instrument, Face Amount $ 1,500,000,000        
Maturity - Maximum Date Dec. 31, 2038        
Debt instrument, stated interest rate 6.20%        
Total debt $ 1,482,000,000       1,481,000,000
Senior notes | 4.875% stated rate          
Debt Instrument [Line Items]          
Debt Instrument, Face Amount $ 500,000,000        
Maturity - Maximum Date Dec. 31, 2040        
Debt instrument, stated interest rate 4.875%        
Total debt $ 489,000,000       489,000,000
Senior notes | 3.625% senior notes          
Debt Instrument [Line Items]          
Debt Instrument, Face Amount $ 375,000,000        
Maturity - Maximum Date Dec. 31, 2042        
Debt instrument, stated interest rate 3.625%        
Total debt $ 368,000,000       367,000,000
Senior notes | 3.40% senior notes          
Debt Instrument [Line Items]          
Debt Instrument, Face Amount $ 500,000,000        
Maturity - Maximum Date Dec. 31, 2046        
Debt instrument, stated interest rate 3.40%        
Total debt $ 491,000,000       491,000,000
Senior notes | Floating rate senior notes          
Debt Instrument [Line Items]          
Debt Instrument, Face Amount $ 400,000,000     $ 400,000,000  
Maturity - Maximum Date Dec. 31, 2022        
Total debt $ 398,000,000       0
Senior notes | 8.375% debentures          
Debt Instrument [Line Items]          
Debt Instrument, Face Amount $ 424,000,000        
Maturity - Maximum Date Dec. 31, 2029        
Debt instrument, stated interest rate 8.375%        
Total debt $ 453,000,000       461,000,000
Senior notes | 8.375% debentures          
Debt Instrument [Line Items]          
Debt Instrument, Face Amount $ 276,000,000        
Maturity - Maximum Date Dec. 31, 2030        
Total debt $ 282,000,000       282,000,000
Senior notes | Canadian senior note 2.125%          
Debt Instrument [Line Items]          
Debt Instrument, Face Amount $ 603,000,000 $ 547,000,000 CAD 750    
Maturity - Maximum Date Dec. 31, 2024        
Debt instrument, stated interest rate 2.125% 2.125% 2.125%    
Total debt $ 600,000,000       0
Senior notes | Floating rate senior notes          
Debt Instrument [Line Items]          
Debt Instrument, Face Amount $ 979,000,000        
Maturity - Minimum Date Dec. 31, 2049        
Maturity - Maximum Date Dec. 31, 2067        
Total debt $ 969,000,000       824,000,000
Capital Lease Obligations          
Debt Instrument [Line Items]          
Debt Instrument, Face Amount $ 450,000,000        
Maturity - Minimum Date Dec. 31, 2017        
Maturity - Maximum Date Dec. 31, 3005        
Total debt $ 450,000,000       447,000,000
Pound Sterling notes | 5.50% notes          
Debt Instrument [Line Items]          
Debt Instrument, Face Amount $ 89,000,000        
Maturity - Maximum Date Dec. 31, 2031        
Debt instrument, stated interest rate 5.50%        
Total debt $ 84,000,000       76,000,000
Pound Sterling notes | 5.125% notes          
Debt Instrument [Line Items]          
Debt Instrument, Face Amount $ 609,000,000        
Maturity - Maximum Date Jan. 01, 2022        
Debt instrument, stated interest rate 5.125%        
Total debt $ 582,000,000       535,000,000
Euro Senior Notes | 1.625% Euro Senior Notes          
Debt Instrument [Line Items]          
Debt Instrument, Face Amount $ 827,000,000        
Debt instrument, stated interest rate 1.625%        
Total debt $ 822,000,000       732,000,000
Euro Senior Notes | 1.00% notes          
Debt Instrument [Line Items]          
Debt Instrument, Face Amount $ 591,000,000        
Debt instrument, stated interest rate 1.00%        
Total debt $ 587,000,000       523,000,000
Euro Senior Notes | Floating rate senior notes          
Debt Instrument [Line Items]          
Debt Instrument, Face Amount 591,000,000        
Total debt 589,000,000       525,000,000
Facility notes and bonds          
Debt Instrument [Line Items]          
Debt Instrument, Face Amount $ 320,000,000        
Maturity - Minimum Date Dec. 31, 2029        
Maturity - Maximum Date Dec. 31, 2045        
Total debt $ 320,000,000       319,000,000
Other debt          
Debt Instrument [Line Items]          
Debt Instrument, Face Amount $ 18,000,000        
Maturity - Minimum Date Dec. 31, 2017        
Maturity - Maximum Date Dec. 31, 2022        
Total debt $ 18,000,000       $ 20,000,000