Basis of Presentation and Significant Accounting Policies (Details) $ / shares in Units, $ in Millions					3 Months Ended	9 Months Ended		12 Months Ended	18 Months Ended
		Jul. 30, 2019 USD ($) $ / shares	Jul. 01, 2019 USD ($)	Jan. 01, 2019 USD ($) Accounting_standard	Sep. 29, 2019 USD ($)	Sep. 29, 2019 USD ($) Operating_Segment	Sep. 30, 2018 USD ($)	Dec. 31, 2018 USD ($) Operating_Segment	Jul. 02, 2019 USD ($)	Jun. 28, 2020	Jan. 01, 2018 Accounting_standard
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of business segments | Operating_Segment						3		2
Number of accounting standards adopted | Accounting_standard				4							11
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Payment to acquire business, net of cash acquired	[1]					$ 10,861	$ 0
ROU assets					$ 1,306	1,306
Lease liabilities (long-term)					1,037	1,037
Accrued rebates and other accruals					5,557	5,557		$ 5,426
Variable lease payments					$ 74	$ 192
Accounting Standards Update 2016-02 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
ROU assets				$ 1,400
Lease liabilities (long-term)				1,400
Cumulative effect adjustment to retained earnings, pre-tax				30
Cumulative effect adjustment to retained earnings, after-tax				$ 20
Minimum [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease term					1 year	1 year
Operating lease term, option to extend						5 years
Maximum [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease term					30 years	30 years
Operating lease term, option to extend						10 years
Array [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Business acquisition, per share in cash (in dollars per share) | $ / shares		$ 48
Payments for acquisition, cash portion		$ 11,200
Payment to acquire business, net of cash acquired		$ 10,900
Upjohn And Mylan [Member] | Forecast [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Ownership percentage										57.00%
Upjohn And Mylan [Member] | Mylan [Member] | Forecast [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Ownership percentage by noncontrolling owners										43.00%
Therachon Asset Acquisition [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Upfront payment			$ 340
Maximum potential milestone payments			$ 470
Fair value of consideration transferred									$ 322

[1] Amounts may not add due to rounding.