Debt - Additional Information (Detail) | Aug. 05, 2020 | May 05, 2020USD ($) | May 04, 2020 | Sep. 30, 2020USD ($) | Sep. 30, 2019USD ($) | Sep. 30, 2020EUR (€) | Sep. 30, 2020USD ($) | Aug. 14, 2020USD ($) | Jul. 14, 2020USD ($) | Mar. 18, 2020USD ($) | Dec. 31, 2019EUR (€) | Dec. 31, 2019USD ($) |
Debt Instrument [Line Items] | | | | | | | | | | | | |
Revolving credit facility repayments | | | | $ 2,022,000,000 | $ 0 | | | | | | | |
Revolving Credit Facility | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | |
Credit facility | | | | | | | $ 2,000,000,000 | | | $ 1,900,000,000 | | |
Credit facility borrowings outstanding | | | | | | | | | | | | $ 0 |
Letters of credit issued under the credit facility | | | | | | | 17,000,000 | | | | | 16,000,000 |
Uncommitted Credit Facility | International Subsidiary One | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | |
Credit facility | € | | | | | | € 50,000,000 | | | | | | |
Credit facility borrowings outstanding | € | | | | | | € 0 | | | | | € 0 | |
Senior Notes | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | |
Accrued interest related to senior notes | | | | | | | 107,000,000 | | | | | 76,000,000 |
Fair value of senior notes | | | | | | | $ 8,600,000,000 | | | | | $ 5,100,000,000 |
Upon the occurrence of certain change of control triggering events | Senior Notes | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | |
Debt instrument redemption price percentage | | | | 101.00% | | | | | | | | |
5.95% senior notes due 2020 | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | |
Senior unsecured notes principal amount | | | | | | | | $ 750,000,000 | | | | |
Debt, interest rate (percentage) | | | | | | 5.95% | 5.95% | 5.95% | | | 5.95% | 5.95% |
2.5% (€650 million) senior notes due 2022 | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | |
Senior unsecured notes principal amount | € | | | | | | € 650,000,000 | | | | | € 650,000,000 | |
Debt, interest rate (percentage) | | | | | | 2.50% | 2.50% | | | | 2.50% | 2.50% |
3.6% senior notes due 2023 | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | |
Debt, interest rate (percentage) | | | | | | 3.60% | 3.60% | | | | | |
3.6% senior notes due 2023 | Unsecured Senior Notes | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | |
Senior unsecured notes principal amount | | | | | | | | | $ 500,000,000 | | | |
Debt, interest rate (percentage) | | | | | | | | | 3.60% | | | |
Senior notes issued price percentage | | | | | | | | | 99.922% | | | |
Additional interest if certain obligations are not satisfied | | | | | | 0.0025 | 0.0025 | | | | | |
4.5% senior notes due 2024 | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | |
Debt, interest rate (percentage) | | | | | | 4.50% | 4.50% | | | | 4.50% | 4.50% |
6.25% senior notes due 2025 | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | |
Debt, interest rate (percentage) | | | | | | 6.25% | 6.25% | | | | | |
6.25% senior notes due 2025 | Unsecured Senior Notes | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | |
Senior unsecured notes principal amount | | $ 2,000,000,000 | | | | | | | | | | |
Debt, interest rate (percentage) | | 6.25% | | | | | | | | | | |
Debt instrument redemption price percentage | | 100.00% | | | | | | | | | | |
7.0% senior notes due 2025 | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | |
Debt, interest rate (percentage) | | | | | | 7.00% | 7.00% | | | | | |
7.0% senior notes due 2025 | Unsecured Senior Notes | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | |
Senior unsecured notes principal amount | | $ 750,000,000 | | | | | | | | | | |
Debt, interest rate (percentage) | | 7.00% | | | | | | | | | | |
Debt instrument redemption price percentage | | 100.00% | | | | | | | | | | |
7.0% senior notes due 2025 | Unsecured Senior Notes | Maximum | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | |
Percentage of principal amount redeemed | | 40.00% | | | | | | | | | | |
5.0% senior notes due 2026 | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | |
Debt, interest rate (percentage) | | | | | | 5.00% | 5.00% | | | | 5.00% | 5.00% |
4.625% senior notes due 2027 | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | |
Debt, interest rate (percentage) | | | | | | 4.625% | 4.625% | | | | | |
4.625% senior notes due 2027 | Unsecured Senior Notes | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | |
Senior unsecured notes principal amount | | | | | | | | | $ 750,000,000 | | | |
Debt, interest rate (percentage) | | | | | | | | | 4.625% | | | |
Senior notes issued price percentage | | | | | | | | | 99.997% | | | |
Additional interest if certain obligations are not satisfied | | | | | | 0.0025 | 0.0025 | | | | | |
3.8% senior notes due 2028 | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | |
Debt, interest rate (percentage) | | | | | | 3.80% | 3.80% | | | | 3.80% | 3.80% |
3.25% senior notes due 2030 | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | |
Debt, interest rate (percentage) | | | | | | 3.25% | 3.25% | | | | 3.25% | 3.25% |
Foreign Credit Facility | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | |
Credit facility borrowings outstanding | | | | | | | $ 0 | | | | | |
Additional borrowing capacity | | | | | | | $ 855,000,000 | | | | | |
Revolving credit facility repayments | | | | $ 772,000,000 | | | | | | | | |
Foreign Credit Facility | Upon the occurrence of certain change of control triggering events | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | |
Debt instrument, covenant, leverage ratio, maximum | 5 | | | | | | | | | | | |
Foreign Credit Facility | Notes prior to November 15, 2029 | Minimum | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | |
Debt, interest rate (percentage) | 1.25% | | | | | | | | | | | |
Foreign Credit Facility | Notes prior to November 15, 2029 | Maximum | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | |
Debt, interest rate (percentage) | 2.00% | | | | | | | | | | | |
Foreign Credit Facility | Eurodollar | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | |
Debt instrument, basis spread on variable rate | 2.50% | | | | | | | | | | | |
Foreign Credit Facility | Base Rate | Notes prior to November 15, 2029 | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | |
Commitment fee on undrawn amounts | 1.50% | | | | | | | | | | | |
Foreign Credit Facility | Base Rate | Notes on or after November 15, 2029 | Minimum | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | |
Debt, interest rate (percentage) | 0.25% | | | | | | | | | | | |
Foreign Credit Facility | Base Rate | Notes on or after November 15, 2029 | Maximum | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | |
Debt, interest rate (percentage) | 1.00% | | | | | | | | | | | |
Amended Credit Facility Maturing on May 31, 2023 | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | |
Debt, interest rate (percentage) | | | | | | 2.41% | 2.41% | | | | | |
Credit facility | | | | | | | $ 2,000,000,000 | | | | | |
Credit facility borrowings outstanding | | | | | | | $ 650,000,000 | | | | | |
Commitment fee on undrawn amounts | | | 2.25% | | | | | | | | | |
Revolving credit facility repayments | | | | $ 478,000,000 | | | | | | | | |
Amended Credit Facility Maturing on May 31, 2023 | Upon the occurrence of certain change of control triggering events | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | |
Debt instrument, covenant, leverage ratio, maximum | | | 5 | | | | | | | | | |
Amended Credit Facility Maturing on May 31, 2023 | Notes prior to November 15, 2029 | Minimum | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | |
Debt, interest rate (percentage) | | | 1.00% | | | | | | | | | |
Amended Credit Facility Maturing on May 31, 2023 | Notes prior to November 15, 2029 | Maximum | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | |
Debt, interest rate (percentage) | | | 1.75% | | | | | | | | | |
Amended Credit Facility Maturing on May 31, 2023 | Base Rate | Notes prior to November 15, 2029 | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | |
Commitment fee on undrawn amounts | | | 1.25% | | | | | | | | | |
Amended Credit Facility Maturing on May 31, 2023 | Base Rate | Notes on or after November 15, 2029 | Minimum | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | |
Debt, interest rate (percentage) | | | 0.00% | | | | | | | | | |
Amended Credit Facility Maturing on May 31, 2023 | Base Rate | Notes on or after November 15, 2029 | Maximum | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | |
Debt, interest rate (percentage) | | | 0.75% | | | | | | | | | |