Summary of Significant Accounting Policies - Narrative (Details) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2017 USD ($)	Dec. 29, 2019 USD ($) Employee Segment	Dec. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)	Jan. 01, 2018 USD ($)
Concentration of Credit Risk [Line Items]
Accrued Rebates Returns And Promotions		$ 10,883	$ 9,380
Number of employees | Employee		132,200
Number of business segments | Segment		3
Deferred taxes on income		$ 7,819	7,640
Other assets		5,695	4,182
Retained earnings		$ 110,659	$ 106,216
Minimum reverse repurchase agreement collateral (as a percent)		102.00%
Sales return reserve (as a percent)		1.00%	1.00%	1.00%
Percentage of profit share payments (less than)		2.00%	2.00%	2.00%
Cost of products sold		$ 27,556	$ 27,091	$ 25,439
Shipping and handling costs as a percent of sales		0.50%
Advertising expense		$ 2,200	2,600	2,500
Provisional toll tax charge	$ 10,100
Deferred tax liability foreign taxes	4,500	$ 1,289	2,240	4,500
Deferred tax asset offset	$ 1,100			1,100
Minimum | Software Development
Concentration of Credit Risk [Line Items]
Estimated useful lives of the assets		3 years
Maximum | Software Development
Concentration of Credit Risk [Line Items]
Estimated useful lives of the assets		8 years
R&D Expense
Concentration of Credit Risk [Line Items]
Concentration risk (as a percent)		5.00%
Retained Earnings
Concentration of Credit Risk [Line Items]
Cumulative effect adjustment					$ (254)
Retained Earnings | ASU 2014-09 - Revenue from Contracts with Customers
Concentration of Credit Risk [Line Items]
Cumulative effect adjustment					(47)
Retained Earnings | ASU 2016-01 - Financial Instruments
Concentration of Credit Risk [Line Items]
Cumulative effect adjustment					232
Retained Earnings | ASU 2016-16 - Income Taxes: Intra-Entity Transfers
Concentration of Credit Risk [Line Items]
Cumulative effect adjustment					$ (439)
Shipping and Handling
Concentration of Credit Risk [Line Items]
Cost of products sold		$ 1,000	1,100	$ 1,000
Pharmaceutical
Concentration of Credit Risk [Line Items]
Accrued Rebates Returns And Promotions		$ 7,000	$ 5,800