Supplemental Equity and Comprehensive Income Information - AOCI rf (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
AOCI Attributable to 3M, Net of Tax Roll Forward
Balance at the beginning of the period	$ 12,931	$ 10,126
Other comprehensive income (loss), before tax:
Balance at the end of the period	13,828	10,214
Cumulative Translation Adjustment
AOCI Attributable to 3M, Net of Tax Roll Forward
Balance at the beginning of the period	(1,450)	(1,899)
Other comprehensive income (loss), before tax:
Amounts before reclassifications	(176)	(439)
Total other comprehensive income (loss), before tax	(176)	(439)
Tax effect	(47)	(2)
Total other comprehensive income (loss), net of tax	(223)	(441)
Balance at the end of the period	(1,673)	(2,340)
Defined Pension and Postretirement Plans Adjustment
AOCI Attributable to 3M, Net of Tax Roll Forward
Balance at the beginning of the period	(6,098)	(6,204)
Other comprehensive income (loss), before tax:
Amounts reclassified out	159	150
Total other comprehensive income (loss), before tax	159	150
Tax effect	(40)	(42)
Total other comprehensive income (loss), net of tax	119	108
Balance at the end of the period	(5,979)	(6,096)
Cash Flow Hedging Instruments, Unrealized Gain (Loss)
AOCI Attributable to 3M, Net of Tax Roll Forward
Balance at the beginning of the period	(173)	(31)
Other comprehensive income (loss), before tax:
Amounts before reclassifications	66	77
Amounts reclassified out	9	(16)
Total other comprehensive income (loss), before tax	75	61
Tax effect	(17)	(14)
Total other comprehensive income (loss), net of tax	58	47
Balance at the end of the period	(115)	16
Retained Earnings
AOCI Attributable to 3M, Net of Tax Roll Forward
Balance at the beginning of the period	43,821	42,130
Other comprehensive income (loss), before tax:
Balance at the end of the period	44,255	42,356
Total Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to 3M, Net of Tax Roll Forward
Balance at the beginning of the period	(7,721)	(8,134)
Other comprehensive income (loss), before tax:
Amounts before reclassifications	(110)	(362)
Amounts reclassified out	168	134
Total other comprehensive income (loss), before tax	58	(228)
Tax effect	(104)	(58)
Total other comprehensive income (loss), net of tax	(46)	(286)
Balance at the end of the period	$ (7,767)	$ (8,420)