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Marketable Securities - Narrative (Details) | 12 Months Ended
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Dec. 31, 2017 item
Percentage of asset-backed securities rated AAA/A-1+, Aaa/P-1, or AAA/F1+ | 90.00%
Number of rating agencies for asset backed securities that must be either Moody's or Standard and Poor's | 1
Minimum |
Number of rating agencies for which asset backed securities must be rated | 2

X
- Definition Percentage of asset-backed securities in the available for sale portfolio that were rated AAA or A-1+ by Standard and Poor's and/or Aaa or P-1 by Moody's and/or AAA or F1+ by Fitch. + References No definition available. + Details
Name: | mmm_AvailableForSaleAssetBackedSecuritiesPercentageOfSecuritiesRatedAtHighestGradeDisclosure
Namespace Prefix: | mmm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition The number of credit rating agencies for which asset-backed securities must be rated. + References No definition available. + Details
Name: | mmm_NumberOfCreditAgencyRatingsNeededAssetBackedSecurities
Namespace Prefix: | mmm_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition The minimal number of credit rating agencies for asset backed securities that must be either Moody's or Standard and Poors. + References No definition available. + Details
Name: | mmm_NumberOfSpecificCreditRatingAgenciesNeededAssetBackedSecurities
Namespace Prefix: | mmm_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |