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Financial Instruments - Narrative (Details) | 12 Months Ended |
--- | --- | ---
Dec. 31, 2018 USD ($) interest_rate_swap | Dec. 31, 2017 USD ($) | May 31, 2018 USD ($) interest_rate_swap
Derivative [Line Items] |  |  |
Number of interest rate swaps held | interest_rate_swap | 19 |  |
Notional amount of derivative | $ 29,742,000,000 | $ 25,595,000,000 |
Pre tax net unrealized gain (loss) on derivatives maturing within next 12 months estimated to be reclassified from AOCI to sales | 186,000,000 |  |
Equity investments without readily determinable fair values | 568,000,000 |  |
Unrealized gains based on favorable observable price changes | 167,000,000 |  |
Unrealized loss related to unfavorable observable price changes | 26,000,000 |  |
Available-for-sale debt securities included in Short-term investments | 894,000,000 |  |
Available-for-sale debt securities maturing within five years | 5,800,000,000 |  |
Cash and cash equivalents | 7,965,000,000 | 6,092,000,000 |
Payments of contingent consideration | 244,000,000 | 100,000,000 |
Fair value of loans payable and long-term debt, including current portion | 25,600,000,000 | 25,600,000,000 |
Carrying value of loans payable and long-term debt, including current portion | 25,100,000,000 | 24,400,000,000 |
Cash collateral received from counterparties | $ 107,000,000 | 3,000,000 |
Customer Concentration Risk | Accounts Receivable | McKesson Corporation, AmerisourceBergen Corporation and Cardinal Health, Inc. [Member] |  |  |
Derivative [Line Items] |  |  |
Percentage of accounts receivable represented by customers with largest balances (as percent) | 40.00% |  |
Afferent Pharmaceuticals |  |  |
Derivative [Line Items] |  |  |
Payments of contingent consideration | $ 175,000,000 |  |
Significant Other Observable Inputs (Level 2) |  |  |
Derivative [Line Items] |  |  |
Cash and cash equivalents | 8,000,000,000 |  |
Cash equivalents | $ 7,200,000,000 |  |
1.30% notes due 2018 | Interest Rate Swap |  |  |
Derivative [Line Items] |  |  |
Number of interest rate swaps held | interest_rate_swap |  |  | 4
Notional amount of derivative |  |  | $ 1,000,000,000
Face amount of debt |  |  | $ 1,000,000,000.0
Fixed-rate notes, stated interest rate (as percent) |  |  | 1.30%
5.00% notes due 2019 | Interest Rate Swap |  |  |
Derivative [Line Items] |  |  |
Number of interest rate swaps held | interest_rate_swap | 3 |  |
Notional amount of derivative | $ 550,000,000 |  |
Face amount of debt | $ 1,250,000,000.00 |  |
Fixed-rate notes, stated interest rate (as percent) | 5.00% |  |
Derivatives Designated as Hedging Instruments |  |  |
Derivative [Line Items] |  |  |
Notional amount of derivative | $ 14,390,000,000 | 14,386,000,000 |
Derivatives Not Designated as Hedging Instruments |  |  |
Derivative [Line Items] |  |  |
Notional amount of derivative | $ 15,352,000,000 | $ 11,209,000,000 |
Maximum | Derivatives Designated as Hedging Instruments |  |  |
Derivative [Line Items] |  |  |
Maximum planning cycle of third-party sales hedges (no more than) | 2 years |  |
Maximum | Derivatives Not Designated as Hedging Instruments |  |  |
Derivative [Line Items] |  |  |
Maximum planning cycle of third-party sales hedges (no more than) | 1 year |  |

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