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Significant Accounting Policies (Long-Lived Assets) (Details) $ in Millions	Dec. 31, 2021 USD ($)
MLMC
Impaired Assets to be Disposed of by Method Other than Sale [Line Items]
Long-lived assets	$ 136

X

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_ImpairedAssetsToBeDisposedOfByMethodOtherThanSaleLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Long-lived assets other than financial instruments, long-term customer relationships of a financial institution, mortgage and other servicing rights, deferred policy acquisition costs, and deferred tax assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 41
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e9038-108599

+ Details

Name:	us-gaap_NoncurrentAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Details

Name:	us-gaap_SubsegmentsAxis=nacco_MississippiLigniteMiningCompanyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: