Long-term Obligations and Borrowing Arrangements - Senior Unsecured Notes (Details) - USD ($) $ in Millions | Mar. 31, 2020 | Dec. 31, 2019 |
Debt Instrument [Line Items] | | | |
Long-term debt | $ 12,529 | | $ 13,174 |
Senior Notes | | | |
Debt Instrument [Line Items] | | | |
Long term debt, carrying value | 11,725 | | 11,975 |
Unamortized discounts and debt issuance costs | (166) | | (173) |
Long-term debt | $ 11,559 | | 11,802 |
Senior Notes | 2020 Notes(1) | | | |
Debt Instrument [Line Items] | | | |
Interest rate | 2.00% | | |
Long term debt, carrying value | $ 0 | [1] | 250 |
Senior Notes | 2021 Merger Notes | | | |
Debt Instrument [Line Items] | | | |
Interest rate | 3.551% | | |
Long term debt, carrying value | $ 1,750 | | 1,750 |
Senior Notes | 2021-A Notes | | | |
Debt Instrument [Line Items] | | | |
Interest rate | 3.20% | | |
Long term debt, carrying value | $ 250 | | 250 |
Senior Notes | 2021-B Notes | | | |
Debt Instrument [Line Items] | | | |
Interest rate | 2.53% | | |
Long term debt, carrying value | $ 250 | | 250 |
Senior Notes | 2022 Notes | | | |
Debt Instrument [Line Items] | | | |
Interest rate | 2.70% | | |
Long term debt, carrying value | $ 250 | | 250 |
Senior Notes | 2023 Merger Notes | | | |
Debt Instrument [Line Items] | | | |
Interest rate | 4.057% | | |
Long term debt, carrying value | $ 2,000 | | 2,000 |
Senior Notes | 2023 Notes | | | |
Debt Instrument [Line Items] | | | |
Interest rate | 3.13% | | |
Long term debt, carrying value | $ 500 | | 500 |
Senior Notes | 2025 Merger Notes | | | |
Debt Instrument [Line Items] | | | |
Interest rate | 4.417% | | |
Long term debt, carrying value | $ 1,000 | | 1,000 |
Senior Notes | 2025 Notes | | | |
Debt Instrument [Line Items] | | | |
Interest rate | 3.40% | | |
Long term debt, carrying value | $ 500 | | 500 |
Senior Notes | 2026 Notes | | | |
Debt Instrument [Line Items] | | | |
Interest rate | 2.55% | | |
Long term debt, carrying value | $ 400 | | 400 |
Senior Notes | 2027 Notes | | | |
Debt Instrument [Line Items] | | | |
Interest rate | 3.43% | | |
Long term debt, carrying value | $ 500 | | 500 |
Senior Notes | 2028 Merger Notes | | | |
Debt Instrument [Line Items] | | | |
Interest rate | 4.597% | | |
Long term debt, carrying value | $ 2,000 | | 2,000 |
Senior Notes | 2038 Merger Notes | | | |
Debt Instrument [Line Items] | | | |
Interest rate | 4.985% | | |
Long term debt, carrying value | $ 500 | | 500 |
Senior Notes | 2038 Notes | | | |
Debt Instrument [Line Items] | | | |
Interest rate | 7.45% | | |
Long term debt, carrying value | $ 125 | | 125 |
Senior Notes | 2045 Notes | | | |
Debt Instrument [Line Items] | | | |
Interest rate | 4.50% | | |
Long term debt, carrying value | $ 550 | | 550 |
Senior Notes | 2046 Notes | | | |
Debt Instrument [Line Items] | | | |
Interest rate | 4.42% | | |
Long term debt, carrying value | $ 400 | | 400 |
Senior Notes | 2048 Merger Notes | | | |
Debt Instrument [Line Items] | | | |
Interest rate | 5.085% | | |
Long term debt, carrying value | $ 750 | | 750 |
Level 2 | Nonrecurring | Senior Notes | | | |
Debt Instrument [Line Items] | | | |
Long-term debt, fair value | 12,358 | | 12,898 |
Level 2 | Nonrecurring | Senior Notes | 2020 Notes(1) | | | |
Debt Instrument [Line Items] | | | |
Long-term debt, fair value | 0 | [1] | 250 |
Level 2 | Nonrecurring | Senior Notes | 2021 Merger Notes | | | |
Debt Instrument [Line Items] | | | |
Long-term debt, fair value | 1,766 | | 1,785 |
Level 2 | Nonrecurring | Senior Notes | 2021-A Notes | | | |
Debt Instrument [Line Items] | | | |
Long-term debt, fair value | 250 | | 254 |
Level 2 | Nonrecurring | Senior Notes | 2021-B Notes | | | |
Debt Instrument [Line Items] | | | |
Long-term debt, fair value | 247 | | 251 |
Level 2 | Nonrecurring | Senior Notes | 2022 Notes | | | |
Debt Instrument [Line Items] | | | |
Long-term debt, fair value | 247 | | 251 |
Level 2 | Nonrecurring | Senior Notes | 2023 Merger Notes | | | |
Debt Instrument [Line Items] | | | |
Long-term debt, fair value | 2,075 | | 2,110 |
Level 2 | Nonrecurring | Senior Notes | 2023 Notes | | | |
Debt Instrument [Line Items] | | | |
Long-term debt, fair value | 504 | | 514 |
Level 2 | Nonrecurring | Senior Notes | 2025 Merger Notes | | | |
Debt Instrument [Line Items] | | | |
Long-term debt, fair value | 1,059 | | 1,090 |
Level 2 | Nonrecurring | Senior Notes | 2025 Notes | | | |
Debt Instrument [Line Items] | | | |
Long-term debt, fair value | 507 | | 521 |
Level 2 | Nonrecurring | Senior Notes | 2026 Notes | | | |
Debt Instrument [Line Items] | | | |
Long-term debt, fair value | 387 | | 400 |
Level 2 | Nonrecurring | Senior Notes | 2027 Notes | | | |
Debt Instrument [Line Items] | | | |
Long-term debt, fair value | 503 | | 520 |
Level 2 | Nonrecurring | Senior Notes | 2028 Merger Notes | | | |
Debt Instrument [Line Items] | | | |
Long-term debt, fair value | 2,184 | | 2,253 |
Level 2 | Nonrecurring | Senior Notes | 2038 Merger Notes | | | |
Debt Instrument [Line Items] | | | |
Long-term debt, fair value | 559 | | 587 |
Level 2 | Nonrecurring | Senior Notes | 2038 Notes | | | |
Debt Instrument [Line Items] | | | |
Long-term debt, fair value | 187 | | 167 |
Level 2 | Nonrecurring | Senior Notes | 2045 Notes | | | |
Debt Instrument [Line Items] | | | |
Long-term debt, fair value | 580 | | 605 |
Level 2 | Nonrecurring | Senior Notes | 2046 Notes | | | |
Debt Instrument [Line Items] | | | |
Long-term debt, fair value | 417 | | 435 |
Level 2 | Nonrecurring | Senior Notes | 2048 Merger Notes | | | |
Debt Instrument [Line Items] | | | |
Long-term debt, fair value | $ 886 | | $ 905 |
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[1] | On January 15, 2020, the Company repaid the 2020 Notes at maturity, using commercial paper notes. |