Financial Instruments - Long-Term Debt (Details) - USD ($) $ in Millions		9 Months Ended
		Sep. 27, 2020	Sep. 29, 2019	Dec. 31, 2019
Debt Instrument [Line Items]
Net fair value adjustments related to hedging and purchase accounting		$ 0		$ 5
Net unamortized discounts, premiums and debt issuance costs		(4)		(43)
Total long-term debt, carried at historical proceeds, as adjusted		49,785		35,955
Current portion of long-term debt, carried at historical proceeds, as adjusted (not included above)		2,149		1,462
Proceeds from issuance of long-term debt		16,700	$ 4,942
Unsecured Debt [Member]
Debt Instrument [Line Items]
Total long-term debt, principal amount	[1]	48,473		34,820
Net fair value adjustments related to hedging and purchase accounting		1,621		1,305
Net unamortized discounts, premiums and debt issuance costs		(314)		(176)
Other long-term debt		5		5
Total long-term debt, carried at historical proceeds, as adjusted		49,785		35,955
Current portion of long-term debt, carried at historical proceeds, as adjusted (not included above)		2,149		$ 1,462
Subsidiaries [Member] | Upjohn Inc [Member]
Debt Instrument [Line Items]
Proceeds from issuance of long-term debt		$ 11,400

[1] As of September 27, 2020, $11.4 billion of proceeds from the Upjohn debt transactions are invested in money market funds and included in Restricted short-term investments in the condensed consolidated balance sheet.