Supplemental Equity and Comprehensive Income Information - AOCI rf (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
AOCI Attributable to 3M, Net of Tax Roll Forward
Balance at the beginning of the period	$ 13,828	$ 10,214	$ 12,931	$ 10,126
Other comprehensive income (loss), before tax:
Balance at the end of the period	14,516	10,925	14,516	10,925
Cumulative Translation Adjustment
AOCI Attributable to 3M, Net of Tax Roll Forward
Balance at the beginning of the period	(1,673)	(2,340)	(1,450)	(1,899)
Other comprehensive income (loss), before tax:
Amounts before reclassifications	159	104	(17)	(335)
Total other comprehensive income (loss), before tax	159	104	(17)	(335)
Tax effect	12	2	(35)
Total other comprehensive income (loss), net of tax	171	106	(52)	(335)
Balance at the end of the period	(1,502)	(2,234)	(1,502)	(2,234)
Defined Pension and Postretirement Plans Adjustment
AOCI Attributable to 3M, Net of Tax Roll Forward
Balance at the beginning of the period	(5,979)	(6,096)	(6,098)	(6,204)
Other comprehensive income (loss), before tax:
Amounts before reclassifications		(80)		(80)
Amounts reclassified out	160	147	319	297
Total other comprehensive income (loss), before tax	160	67	319	217
Tax effect	(39)	(20)	(79)	(62)
Total other comprehensive income (loss), net of tax	121	47	240	155
Balance at the end of the period	(5,858)	(6,049)	(5,858)	(6,049)
Cash Flow Hedging Instruments, Unrealized Gain (Loss)
AOCI Attributable to 3M, Net of Tax Roll Forward
Balance at the beginning of the period	(115)	16	(173)	(31)
Other comprehensive income (loss), before tax:
Amounts before reclassifications	(26)	(15)	40	62
Amounts reclassified out	12	(31)	21	(47)
Total other comprehensive income (loss), before tax	(14)	(46)	61	15
Tax effect	3	10	(14)	(4)
Total other comprehensive income (loss), net of tax	(11)	(36)	47	11
Balance at the end of the period	(126)	(20)	(126)	(20)
Retained Earnings
AOCI Attributable to 3M, Net of Tax Roll Forward
Balance at the beginning of the period	44,255	42,356	43,821	42,130
Other comprehensive income (loss), before tax:
Balance at the end of the period	44,824	42,786	44,824	42,786
Total Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to 3M, Net of Tax Roll Forward
Balance at the beginning of the period	(7,767)	(8,420)	(7,721)	(8,134)
Other comprehensive income (loss), before tax:
Amounts before reclassifications	133	9	23	(353)
Amounts reclassified out	172	116	340	250
Total other comprehensive income (loss), before tax	305	125	363	(103)
Tax effect	(24)	(8)	(128)	(66)
Total other comprehensive income (loss), net of tax	281	117	235	(169)
Balance at the end of the period	$ (7,486)	$ (8,303)	$ (7,486)	$ (8,303)