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Financial Instruments - Narrative (Details) | 3 Months Ended | 12 Months Ended |  |
--- | --- | --- | --- | ---
Dec. 31, 2020 USD ($) | Dec. 31, 2019 USD ($) | Dec. 31, 2020 USD ($) | Dec. 31, 2019 USD ($) | Jun. 30, 2020 USD ($) | Feb. 29, 2020 USD ($) interest_rate_swap
Derivative [Line Items] |  |  |  |  |  |
Notional amount of derivative | $ 32,784,000,000 | $ 30,666,000,000 | $ 32,784,000,000 | $ 30,666,000,000 |  |
Face amount of debt |  |  |  |  | $ 4,500,000,000 |
Pre tax net unrealized gain (loss) on derivatives maturing within next 12 months estimated to be reclassified from AOCI to sales |  |  | (331,000,000) |  |  |
Equity investments without readily determinable fair values | 586,000,000 | 420,000,000 | 586,000,000 | 420,000,000 |  |
Unrealized gains based on favorable observable price changes |  |  | 62,000,000 | 20,000,000 |  |
Unrealized loss related to unfavorable observable price changes |  |  | 3,000,000 | 13,000,000 |  |
Cumulative upward price adjustment | 169,000,000 |  | 169,000,000 |  |  |
Cumulative downward price adjustment | 24,000,000 |  | 24,000,000 |  |  |
Payments of contingent consideration |  |  | 106,000,000 | 85,000,000 |  |
Fair value of loans payable and long-term debt, including current portion | 36,000,000,000.0 | 28,800,000,000 | 36,000,000,000.0 | 28,800,000,000 |  |
Long term and short term debt | 31,800,000,000 | 26,300,000,000 | 31,800,000,000 | 26,300,000,000 |  |
Accounts receivable factored | 2,300,000,000 | 2,700,000,000 |  |  |  |
Funds collected from factoring of receivable, held in restricted cash | 102,000,000 | 256,000,000 | 102,000,000 | 256,000,000 |  |
Cash collateral received from counterparties | 0 | 34,000,000 | 0 | 34,000,000 |  |
Right to reclaim cash | 36,000,000 | 0 | $ 36,000,000 | 0 |  |
1.85% Notes Due 2020 [Member] |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |
Face amount of debt |  |  |  |  |  | $ 1,250,000,000
Fixed-rate notes, stated interest rate (as percent) |  |  |  |  |  | 1.85%
Customer Concentration Risk | Accounts Receivable | McKesson Corporation, AmerisourceBergen Corporation and Cardinal Health, Inc. |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |
Percentage of accounts receivable represented by customers with largest balances (as percent) |  |  | 45.00% |  |  |
Level 2 |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |
Cash equivalents | 6,800,000,000 | 8,900,000,000 | $ 6,800,000,000 | 8,900,000,000 |  |
Interest Rate Swap |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |
Number of interest rate swaps held | interest_rate_swap |  |  |  |  |  | 5
Notional amount of derivative |  |  |  |  |  | $ 250,000,000
Derivatives Designated as Hedging Instruments |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |
Notional amount of derivative | 13,714,000,000 | 14,728,000,000 | 13,714,000,000 | 14,728,000,000 |  |
Derivatives Not Designated as Hedging Instruments |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |
Notional amount of derivative | $ 19,070,000,000 | $ 15,938,000,000 | $ 19,070,000,000 | $ 15,938,000,000 |  |
Maximum | Derivatives Designated as Hedging Instruments |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |
Maximum planning cycle of hedges (no more than) |  |  | 2 years |  |  |
Maximum | Derivatives Not Designated as Hedging Instruments |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |
Maximum planning cycle of hedges (no more than) |  |  | 1 year |  |  |

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