Basis of Presentation and Significant Accounting Policies - Summary of Change in Accounting Principle (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Oct. 03, 2021	Sep. 27, 2020	Oct. 03, 2021	Sep. 27, 2020	Dec. 31, 2020
Condensed Consolidated Statements of Income:
Other (income)/deductions––net	$ (1,696)	$ 1,878	$ (3,697)	$ 1,114
Income from continuing operations before provision/(benefit) for taxes on income	7,836	570	20,128	6,438
Provision/(benefit) for taxes on income	(331)	(347)	1,518	434
Income/(loss) from discontinued operations––net of tax	(9)	560	24	2,334
Net income before allocation to noncontrolling interests	8,159	1,477	18,633	8,338
Net income attributable to Pfizer Inc. common shareholders	$ 8,146	$ 1,469	$ 18,586	$ 8,313
Earnings per common share––basic:
Income from continuing operations attributable to Pfizer Inc. common shareholders (in dollars per share)	$ 1.45	$ 0.16	$ 3.32	$ 1.08
Income/(loss) from discontinued operations––net of tax (in dollars per share)	0	0.10	0	0.42
Net income attributable to Pfizer Inc. common shareholders (in dollars per share)	1.45	0.26	3.32	1.50
Earnings per common share––diluted:
Income from continuing operations attributable to Pfizer Inc. common shareholders (in dollars per share)	1.42	0.16	3.26	1.06
Income/(loss) from discontinued operations––net of tax (in dollars per share)	0	0.10	0	0.42
Net income attributable to Pfizer Inc. common shareholders (in dollars per share)	$ 1.42	$ 0.26	$ 3.27	$ 1.48
Condensed Consolidated Statements of Comprehensive Income:
Foreign currency translation adjustments, net	$ (866)	$ 1,403	$ (366)	$ (27)
Benefit plans: actuarial gains/(losses), net	0	0	0	0
Reclassification adjustments related to amortization	0	0	0	0
Reclassification adjustments related to settlements, net	0	0	0	0
Other	0	0	0	0
Tax provision/(benefit) on other comprehensive income/(loss)	(65)	(19)	(44)	(311)
Condensed Consolidated Statements of Cash Flows:
Deferred taxes from continuing operations			(3,702)	(735)
Benefit plan contributions in excess of expense/income			(1,933)	(760)
Condensed Consolidated Balance Sheets:
Noncurrent deferred tax assets and other noncurrent tax assets	2,755		2,755		$ 2,383
Other noncurrent assets	6,705		6,705		4,569
Pension benefit obligations	3,676		3,676		4,766
Retained earnings	102,252		102,252		90,392
Accumulated other comprehensive loss	(5,649)		(5,649)		(5,310)
Previous Accounting Principle [Member]
Condensed Consolidated Statements of Income:
Other (income)/deductions––net	(641)	889	(2,414)	232
Income from continuing operations before provision/(benefit) for taxes on income	6,782	1,559	18,845	7,320
Provision/(benefit) for taxes on income	(561)	(104)	1,237	647
Income/(loss) from discontinued operations––net of tax	(9)	539	24	2,374
Net income before allocation to noncontrolling interests	7,334	2,202	17,631	9,046
Net income attributable to Pfizer Inc. common shareholders	$ 7,322	$ 2,194	$ 17,584	$ 9,022
Earnings per common share––basic:
Income from continuing operations attributable to Pfizer Inc. common shareholders (in dollars per share)	$ 1.30	$ 0.30	$ 3.14	$ 1.20
Income/(loss) from discontinued operations––net of tax (in dollars per share)	0	0.10	0	0.43
Net income attributable to Pfizer Inc. common shareholders (in dollars per share)	1.30	0.39	3.14	1.62
Earnings per common share––diluted:
Income from continuing operations attributable to Pfizer Inc. common shareholders (in dollars per share)	1.27	0.29	3.08	1.18
Income/(loss) from discontinued operations––net of tax (in dollars per share)	0	0.10	0	0.42
Net income attributable to Pfizer Inc. common shareholders (in dollars per share)	$ 1.27	$ 0.39	$ 3.09	$ 1.60
Condensed Consolidated Statements of Comprehensive Income:
Foreign currency translation adjustments, net	$ (961)	$ 1,609	$ (354)	$ 96
Benefit plans: actuarial gains/(losses), net	836	(1,211)	881	(1,372)
Reclassification adjustments related to amortization	74	67	222	200
Reclassification adjustments related to settlements, net	139	174	162	240
Other	95	(206)	(11)	(123)
Tax provision/(benefit) on other comprehensive income/(loss)	(89)	(262)	(20)	(527)
Condensed Consolidated Statements of Cash Flows:
Deferred taxes from continuing operations			(3,983)	(522)
Benefit plan contributions in excess of expense/income			(650)	(1,642)
Condensed Consolidated Balance Sheets:
Noncurrent deferred tax assets and other noncurrent tax assets	3,012		3,012		2,383
Other noncurrent assets	6,687		6,687		4,569
Pension benefit obligations	3,677		3,677		4,766
Retained earnings	101,250		101,250		96,770
Accumulated other comprehensive loss	(4,408)		(4,408)		(11,688)
Impact of Change [Member]
Condensed Consolidated Statements of Income:
Other (income)/deductions––net	(1,055)	989	(1,283)	881
Income from continuing operations before provision/(benefit) for taxes on income	1,055	(989)	1,283	(881)
Provision/(benefit) for taxes on income	230	(243)	281	(213)
Income/(loss) from discontinued operations––net of tax	0	21	0	(40)
Net income before allocation to noncontrolling interests	825	(724)	1,002	(709)
Net income attributable to Pfizer Inc. common shareholders	$ 825	$ (724)	$ 1,002	$ (709)
Earnings per common share––basic:
Income from continuing operations attributable to Pfizer Inc. common shareholders (in dollars per share)	$ 0.15	$ (0.13)	$ 0.18	$ (0.12)
Income/(loss) from discontinued operations––net of tax (in dollars per share)	0	0	0	(0.01)
Net income attributable to Pfizer Inc. common shareholders (in dollars per share)	0.15	(0.13)	0.18	(0.13)
Earnings per common share––diluted:
Income from continuing operations attributable to Pfizer Inc. common shareholders (in dollars per share)	0.15	(0.13)	0.18	(0.12)
Income/(loss) from discontinued operations––net of tax (in dollars per share)	0	0	0	(0.01)
Net income attributable to Pfizer Inc. common shareholders (in dollars per share)	$ 0.15	$ (0.13)	$ 0.18	$ (0.13)
Condensed Consolidated Statements of Comprehensive Income:
Foreign currency translation adjustments, net	$ 95	$ (206)	$ (11)	$ (123)
Benefit plans: actuarial gains/(losses), net	(836)	1,211	(881)	1,372
Reclassification adjustments related to amortization	(74)	(67)	(222)	(200)
Reclassification adjustments related to settlements, net	(139)	(174)	(162)	(240)
Other	(95)	206	11	123
Tax provision/(benefit) on other comprehensive income/(loss)	23	$ 243	(24)	215
Condensed Consolidated Statements of Cash Flows:
Deferred taxes from continuing operations			281	(213)
Benefit plan contributions in excess of expense/income			(1,283)	$ 881
Condensed Consolidated Balance Sheets:
Noncurrent deferred tax assets and other noncurrent tax assets	(257)		(257)		0
Other noncurrent assets	18		18		0
Pension benefit obligations	0		0		0
Retained earnings	1,002		1,002		(6,378)
Accumulated other comprehensive loss	$ (1,241)		$ (1,241)		$ 6,378