Business Combination, Transaction Valuation

No definition available.

Name:	cnm_BusinessCombinationTransactionValuation
Namespace Prefix:	cnm_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Partnership Interests, Purchased From Consolidated Entity, Units

+ References

No definition available.

+ Details

Name:	cnm_PartnershipInterestsPurchasedFromConsolidatedEntityUnits
Namespace Prefix:	cnm_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Cash received on stock transaction after deduction of issuance costs.

+ References

No definition available.

+ Details

Name:	us-gaap_SaleOfStockConsiderationReceivedOnTransaction
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The number of shares issued or sold by the subsidiary or equity method investee per stock transaction.

+ References

No definition available.

+ Details

Name:	us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Per share amount received by subsidiary or equity investee for each share of common stock issued or sold in the stock transaction.

+ References

No definition available.

+ Details

Name:	us-gaap_SaleOfStockPricePerShare
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event.

+ References

No definition available.

+ Details

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Data Type:	xbrli:stringItemType
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Period Type:	duration

- Details

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- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessAcquisitionAxis=cnm_LMBagAndSupplyCoIncMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SubsidiarySaleOfStockAxis=us-gaap_OverAllotmentOptionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementClassOfStockAxis=us-gaap_CommonClassAMember
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Data Type:	na
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Subsequent Events (Details) - USD ($) $ / shares in Units, $ in Millions	Aug. 30, 2021	Aug. 20, 2021	Aug. 09, 2021	Jul. 27, 2021
Subsequent Event [Line Items]
Partnership Interests acquired from consolidated entity (in units)				34,883,721
Subsequent event
Subsequent Event [Line Items]
Partnership Interests acquired from consolidated entity (in units)		5,232,558
Subsequent event \| Pacific Pipe
Subsequent Event [Line Items]
Transaction value			$ 102.5
Subsequent event \| L&M
Subsequent Event [Line Items]
Transaction value	$ 60.0
Subsequent event \| Underwriter option
Subsequent Event [Line Items]
Stock offering price (in dollars per share)		$ 20.00
Subsequent event \| Underwriter option \| Class A common stock
Subsequent Event [Line Items]
Number of shares issued (in share)		5,232,558
Stock offering price (in dollars per share)		$ 20.00
Net proceeds after deducting underwriting discounts and commissions		$ 99.5