Basis of Presentation and Significant Accounting Policies (Details) $ in Millions			3 Months Ended			9 Months Ended		12 Months Ended
		Jan. 01, 2018 USD ($) Accounting_standard	Sep. 30, 2018 USD ($)	Apr. 01, 2018 USD ($)	Oct. 01, 2017 USD ($)	Sep. 30, 2018 USD ($) Operating_Segment	Oct. 01, 2017 USD ($)	Dec. 31, 2017 USD ($)
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of business segments | Operating_Segment						2
Number of accounting standards adopted | Accounting_standard		11
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net unrealized gains during the reporting period on equity securities still held at the reporting date	[1]		$ 40			$ 370
Other income	[2]		414		$ (79)	1,143	$ (65)
Net increase in cash, cash equivalents, restricted cash and restricted cash equivalents	[3]					2,227	$ 193
Accrued rebates and other accruals			5,548			5,548		$ 4,923
Financial Assets and Liabilities [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect adjustment to retained earnings, pre-tax		$ 462
Cumulative effect adjustment to retained earnings, after-tax		419
Net unrealized gains during the reporting period on equity securities still held at the reporting date			8			344
Accounting for Hedging Activities [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Other income			$ 23			68
Restricted Cash in the Statement of Cash Flows [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net increase in cash, cash equivalents, restricted cash and restricted cash equivalents						10
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Revenues [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect adjustment to retained earnings, pre-tax		584		$ 584
Cumulative effect adjustment to retained earnings, after-tax		450
Reclassification From Financing Activities To Operating Activities [Member] | Classification of Certain Transactions in the Statement of Cash Flows [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Debt prepayment and extinguishment costs						(7)
Reclassification From Operating Activities To Financing Activities [Member] | Classification of Certain Transactions in the Statement of Cash Flows [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accreted interest						$ 69
Collaboration Arrangements [Member] | Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Revenues [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect adjustment to retained earnings, pre-tax		500
Collaboration Arrangements, Income From Upfront And Pre-Approval Milestone Payments [Member] | Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Revenues [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect adjustment to retained earnings, pre-tax		394
Collaboration Arrangements, Product Manufacturing [Member] | Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Revenues [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect adjustment to retained earnings, pre-tax		82
Product Rights And Out-Licensing Arrangements [Member] | Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Revenues [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect adjustment to retained earnings, pre-tax		394
Product Shipments [Member] | Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Revenues [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect adjustment to retained earnings, pre-tax		84
Sales Revenue, Product Line [Member] | Product Concentration Risk [Member] | Top Nine Products [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Concentration risk, amount								$ 1,000
Concentration risk, percentage								46.00%
Retained Earnings [Member] | Income Tax Accounting [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect adjustment to retained earnings, after-tax		(189)
Retained Earnings [Member] | Reclassification of Certain Tax Effects from AOCI [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect adjustment to retained earnings, after-tax		$ 495

[1] The third quarter of 2018 includes $8 million of unrealized net gains in Other (income)/deductions––net reflecting the adoption of a new accounting standard in the first quarter of 2018 and $32 million of unrealized gains on other equity securities. The first nine months of 2018 includes $344 million of unrealized net gains in Other (income)/deductions––net reflecting the adoption of a new accounting standard in the first quarter of 2018 and $26 million of unrealized gains on other equity securities. For additional information, see Note 1B and Note 4.

[2] Amounts may not add due to rounding.

[3] Amounts may not add due to rounding.