v3.10.0.1
Debt - Summary of Outstanding Long-Term Debt (Detail) - USD ($)
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Debt Instrument [Line Items]    
Debt instrument principal amount $ 7,400,000,000 $ 6,650,000,000
Debt instrument interest rate effective percentage 0.00% 0.00%
Liabilities arising from capital lease transactions $ 27,000,000 $ 29,000,000
Unamortized discounts, premiums and debt issuance costs (31,000,000) (28,000,000)
Fair value of embedded cash conversion option (42,000,000) (86,000,000)
Total debt, including unamortized discounts, premiums, debt issuance costs [and fair value adjustments] 7,354,000,000 6,565,000,000
Long-term debt    
Total debt, including unamortized discounts, premiums, debt issuance costs [and fair value adjustments] 7,354,000,000 6,565,000,000
Current portion of long-term debt (1,107,000,000) (751,000,000)
Long-term debt $ 6,247,000,000 5,814,000,000
Fixed-Rate 3.75% Senior Unsecured Notes Maturing in June 2018 [Member]    
Debt Instrument [Line Items]    
Debt instrument maturity date 2018-06  
Debt instrument principal amount $ 0 $ 750,000,000
Debt instrument interest rate effective percentage 3.75% 3.75%
Fixed-Rate 4.125% Senior Unsecured Notes Maturing in June 2020 [Member]    
Debt Instrument [Line Items]    
Debt instrument maturity date 2020-06  
Debt instrument principal amount $ 600,000,000 $ 600,000,000
Debt instrument interest rate effective percentage 4.125% 4.125%
Fixed-Rate 4.125% Senior Unsecured Notes Maturing in June 2021 [Member]    
Debt Instrument [Line Items]    
Debt instrument maturity date 2021-06  
Debt instrument principal amount $ 1,350,000,000 $ 1,350,000,000
Debt instrument interest rate effective percentage 4.125% 4.125%
Fixed-Rate 4.625% Senior Unsecured Notes Maturing in June 2022 [Member]    
Debt Instrument [Line Items]    
Debt instrument maturity date 2022-06  
Debt instrument principal amount $ 400,000,000 $ 400,000,000
Debt instrument interest rate effective percentage 4.625% 4.625%
Fixed-Rate 3.875% Senior Unsecured Notes Maturing in September 2022 [Member]    
Debt Instrument [Line Items]    
Debt instrument maturity date 2022-09  
Debt instrument principal amount $ 1,000,000,000 $ 1,000,000,000
Debt instrument interest rate effective percentage 3.875% 3.875%
Fixed-Rate 5.75% Senior Unsecured Notes Maturing in March 2023 [Member]    
Debt Instrument [Line Items]    
Debt instrument maturity date 2023-03  
Debt instrument principal amount $ 0 $ 500,000,000
Debt instrument interest rate effective percentage 5.75% 5.75%
Fixed-Rate 4.625% Senior Unsecured Notes Maturing in June 2023 [Member]    
Debt Instrument [Line Items]    
Debt instrument maturity date 2023-06  
Debt instrument principal amount $ 900,000,000 $ 900,000,000
Debt instrument interest rate effective percentage 4.625% 4.625%
Fixed-Rate 4.875% Senior Unsecured Notes Maturing in March 2024 [Member]    
Debt Instrument [Line Items]    
Debt instrument maturity date 2024-03  
Debt instrument principal amount $ 1,000,000,000 $ 0
Debt instrument interest rate effective percentage 4.875% 0.00%
Fixed-Rate 5.35% Senior Unsecured Notes Maturing in March 2026 [Member]    
Debt Instrument [Line Items]    
Debt instrument maturity date 2026-03  
Debt instrument principal amount $ 500,000,000 $ 0
Debt instrument interest rate effective percentage 5.35% 0.00%
Fixed-Rate 5.55% Senior Unsecured Notes Maturing in December 2028 [Member]    
Debt Instrument [Line Items]    
Debt instrument maturity date 2028-12  
Debt instrument principal amount $ 500,000,000 $ 0
Debt instrument interest rate effective percentage 5.55% 0.00%
Fixed-Rate 1% Cash Convertible Notes Maturing in December 2019 [Member]    
Debt Instrument [Line Items]    
Debt instrument maturity date 2019-12  
Debt instrument principal amount $ 1,150,000,000 $ 1,150,000,000
Debt instrument interest rate effective percentage 1.00% 1.00%
Floating-Rate Revolving Credit Facility Maturing in December 2020 [Member]    
Debt Instrument [Line Items]    
Debt instrument maturity date 2020-12  
Debt instrument principal amount $ 0 $ 0
Debt instrument interest rate effective percentage 0.00% 0.00%