Supplemental Equity and Comprehensive Income Information - AOCI rf (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
AOCI Attributable to 3M, Net of Tax Roll Forward
Balance at the beginning of the period	$ 10,126	$ 9,848	$ 11,622
Other comprehensive income (loss), before tax:
Balance at the end of the period	12,931	10,126	9,848
ASU 2016-02 Leases | Cumulative Effect, Period of Adoption, Adjustment
AOCI Attributable to 3M, Net of Tax Roll Forward
Balance at the beginning of the period		14
Other comprehensive income (loss), before tax:
Balance at the end of the period			14
Cumulative Translation Adjustment
AOCI Attributable to 3M, Net of Tax Roll Forward
Balance at the beginning of the period	(1,899)	(2,098)	(1,638)
Other comprehensive income (loss), before tax:
Amounts before reclassifications	387	102	(414)
Amounts reclassified out		142
Total other comprehensive income (loss), before tax	387	244	(414)
Tax effect	62	(32)	(47)
Total other comprehensive income (loss), net of tax	449	212	(461)
Impact from purchase of subsidiary shares			1
Balance at the end of the period	(1,450)	(1,899)	(2,098)
Cumulative Translation Adjustment | ASU 2018-02 Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income | Cumulative Effect, Period of Adoption, Adjustment
AOCI Attributable to 3M, Net of Tax Roll Forward
Balance at the beginning of the period		(13)
Other comprehensive income (loss), before tax:
Balance at the end of the period			(13)
Defined Pension and Postretirement Plans Adjustment
AOCI Attributable to 3M, Net of Tax Roll Forward
Balance at the beginning of the period	(6,209)	(4,832)	(5,276)
Other comprehensive income (loss), before tax:
Amounts before reclassifications	(555)	(1,227)	55
Amounts reclassified out	676	459	606
Total other comprehensive income (loss), before tax	121	(768)	661
Tax effect	50	208	(217)
Total other comprehensive income (loss), net of tax	171	(560)	444
Balance at the end of the period	(6,038)	(6,209)	(4,832)
Defined Pension and Postretirement Plans Adjustment | ASU 2018-02 Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income | Cumulative Effect, Period of Adoption, Adjustment
AOCI Attributable to 3M, Net of Tax Roll Forward
Balance at the beginning of the period		(817)
Other comprehensive income (loss), before tax:
Balance at the end of the period			(817)
Cash Flow Hedging Instruments, Unrealized Gain (Loss)
AOCI Attributable to 3M, Net of Tax Roll Forward
Balance at the beginning of the period	(31)
Other comprehensive income (loss), before tax:
Amounts before reclassifications	(113)	(26)
Amounts reclassified out	(71)	(70)
Total other comprehensive income (loss), before tax	(184)	(96)
Tax effect	42	24
Total other comprehensive income (loss), net of tax	(142)	(72)
Balance at the end of the period	(173)	(31)
Cash Flow Hedging Instruments, Unrealized Gain (Loss)
AOCI Attributable to 3M, Net of Tax Roll Forward
Balance at the beginning of the period		64	(112)
Other comprehensive income (loss), before tax:
Amounts before reclassifications			133
Amounts reclassified out			96
Total other comprehensive income (loss), before tax			229
Tax effect			(53)
Total other comprehensive income (loss), net of tax			176
Balance at the end of the period			64
Cash Flow Hedging Instruments, Unrealized Gain (Loss) | ASU 2018-02 Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income | Cumulative Effect, Period of Adoption, Adjustment
AOCI Attributable to 3M, Net of Tax Roll Forward
Balance at the beginning of the period		(23)
Other comprehensive income (loss), before tax:
Balance at the end of the period			(23)
Retained Earnings
AOCI Attributable to 3M, Net of Tax Roll Forward
Balance at the beginning of the period	42,135	40,636	39,115
Other comprehensive income (loss), before tax:
Balance at the end of the period	43,761	42,135	40,636
Retained Earnings | ASU 2018-02 Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income | Cumulative Effect, Period of Adoption, Adjustment
AOCI Attributable to 3M, Net of Tax Roll Forward
Balance at the beginning of the period		853
Other comprehensive income (loss), before tax:
Balance at the end of the period			853
Retained Earnings | ASU 2016-02 Leases | Cumulative Effect, Period of Adoption, Adjustment
AOCI Attributable to 3M, Net of Tax Roll Forward
Balance at the beginning of the period		14
Other comprehensive income (loss), before tax:
Balance at the end of the period			14
Total Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to 3M, Net of Tax Roll Forward
Balance at the beginning of the period	(8,139)	(6,866)	(7,026)
Other comprehensive income (loss), before tax:
Amounts before reclassifications	(281)	(1,151)	(226)
Amounts reclassified out	605	531	702
Total other comprehensive income (loss), before tax	324	(620)	476
Tax effect	154	200	(317)
Total other comprehensive income (loss), net of tax	478	(420)	159
Impact from purchase of subsidiary shares			1
Balance at the end of the period	$ (7,661)	(8,139)	(6,866)
Total Accumulated Other Comprehensive Income (Loss) | ASU 2018-02 Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income | Cumulative Effect, Period of Adoption, Adjustment
AOCI Attributable to 3M, Net of Tax Roll Forward
Balance at the beginning of the period		$ (853)
Other comprehensive income (loss), before tax:
Balance at the end of the period			$ (853)