Equity Method Investment Units Purchased

No definition available.

Name:	mwh_EquityMethodInvestmentUnitsPurchased
Namespace Prefix:	mwh_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- 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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 808
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479402/808-10-50-1

+ Details

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

- Definition

The cash inflow associated with the amount received from entity's first offering of stock to the public.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 45
-Paragraph 14
-Subparagraph (a)
-SubTopic 10
-Topic 230
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482740/230-10-45-14

+ Details

Name:	us-gaap_ProceedsFromIssuanceInitialPublicOffering
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

Number of shares of stock issued as of the balance sheet date, including shares that had been issued and were previously outstanding but which are now held in the treasury.

+ References

No definition available.

+ Details

Name:	us-gaap_SharesIssued
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Per share or per unit amount of equity securities issued.

+ References

No definition available.

+ Details

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

- Details

Name:	us-gaap_StatementClassOfStockAxis=us-gaap_CommonClassAMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	mwh_SecondaryOfferingShareActivityAxis=mwh_SellingStockholderSharesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	mwh_SecondaryOfferingShareActivityAxis=mwh_CompanyIssuedSharesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

Description of Business - Additional information (Detail) - USD ($) $ / shares in Units, $ in Thousands			6 Months Ended
	Jun. 04, 2026	Feb. 12, 2026	Jun. 30, 2026	Jun. 30, 2025	Jun. 01, 2026
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Proceeds from issuance initial public offering			$ 844,249	$ 0
Equity method investment units purchased	8,396,830	23,575,000
Common Class A [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Shares, issued					15,000,000
Sale of Stock, number of shares issued in transaction		91,773,571
Common Class A [Member] \| Selling stockholder shares
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Shares, issued					7,698,410
Common Class A [Member] \| Company issued shares
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Shares, issued					7,301,590
Shares issued, price per share					$ 36
Common Class A [Member] \| IPO [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Shares, issued		23,575,000
Proceeds from issuance initial public offering		$ 552,500
Common Class A [Member] \| Over-Allotment Option [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Shares, issued	2,250,000
Common Class A [Member] \| Over-Allotment Option [Member] \| Selling stockholder shares
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Shares, issued	1,154,760
Common Class A [Member] \| Over-Allotment Option [Member] \| Company issued shares
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Shares, issued	1,095,240
Shares issued, price per share	$ 36
Common Class B [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Sale of Stock, number of shares issued in transaction		87,141,865