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Financial Instruments - Narrative (Details)	6 Months Ended
Financial Instruments - Narrative (Details)	Jun. 30, 2018 USD ($) interest_rate_swap	May 31, 2018 USD ($) interest_rate_swap	Dec. 31, 2017 USD ($)
Derivative [Line Items]
Number of interest rate swaps held (in interest rate swaps) \| interest_rate_swap	22
Notional amount	$ 25,650,000,000		$ 25,595,000,000
Pretax net unrealized gain on derivatives maturing within next 12 months estimated to be reclassified from AOCI to sales	29,000,000
Equity investments without readily determinable fair values	675,000,000
Unrealized gains of equity investments	129,000,000
Unrealized losses on investments	26,000,000
Available-for-sale debt securities included in Short-term investments	2,300,000,000
Available-for-sale debt securities maturing after one year through five years	9,600,000,000
Cash and cash equivalents	5,310,000,000		6,092,000,000
Fair value of loans payable and long-term debt, including current portion	23,900,000,000		25,600,000,000
Carrying value of loans payable and long-term debt, including current portion	23,300,000,000		24,400,000,000
Accounts receivable outstanding for more than one year	40,000,000
Cash collateral received from counterparties	90,000,000		3,000,000
Cash collateral advanced	0		0
Afferent Pharmaceuticals
Derivative [Line Items]
Payment for contingent consideration	175,000,000
Significant Other Observable Inputs (Level 2)
Derivative [Line Items]
Cash and cash equivalents	5,300,000,000
Cash equivalents	4,500,000,000
1.30% notes due 2018 \| Interest rate swap contracts
Derivative [Line Items]
Number of interest rate swaps held (in interest rate swaps) \| interest_rate_swap		4
Notional amount		$ 250,000,000
Face amount of debt		$ 1,000,000,000.0
Stated interest rate (as percent)		1.30%
Derivatives Designated as Hedging Instruments
Derivative [Line Items]
Notional amount	$ 14,566,000,000		14,386,000,000
Derivatives Designated as Hedging Instruments \| Maximum
Derivative [Line Items]
Maximum average period of maturities of contracts in years (less than)	2 years
Derivatives Not Designated as Hedging Instruments
Derivative [Line Items]
Notional amount	$ 11,084,000,000		$ 11,209,000,000
Derivatives Not Designated as Hedging Instruments \| Maximum
Derivative [Line Items]
Maximum average period of maturities of contracts in years (less than)	1 year