XML 64 R47.htm IDEA: XBRL DOCUMENT v3.21.2

Summary of Significant Accounting Policies (Narrative) (Details) - USD ($)	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Product Warranty Expense	$ 3,500,000	$ 2,600,000	$ 3,900,000
Asset Retirement Obligation	3,800,000
Exposure to Workers Compensation Claims, Per Incident	800,000
Workers' Compensation Liability	$ 10,500,000	$ 6,200,000
Income Tax Benefit, Likelihood of Realization Threshold	50.00%
Debt Issuance Costs, Net	$ 6,600,000
Minimum [Member]
Finite-Lived Tangible Asset, Useful Life, Maximum		3 years
Maximum [Member]
Finite-Lived Tangible Asset, Useful Life, Maximum		10 years
Land Improvements [Member] | Minimum [Member]
Property, Plant and Equipment, Useful Life, Minimum	10 years
Land Improvements [Member] | Maximum [Member]
Property, Plant and Equipment, Useful Life, Minimum	20 years
Building [Member] | Minimum [Member]
Property, Plant and Equipment, Useful Life, Minimum	10 years
Building [Member] | Maximum [Member]
Property, Plant and Equipment, Useful Life, Minimum	40 years
Machinery and Equipment [Member] | Minimum [Member]
Property, Plant and Equipment, Useful Life, Minimum	3 years
Machinery and Equipment [Member] | Maximum [Member]
Property, Plant and Equipment, Useful Life, Minimum	15 years
Software and Software Development Costs [Member] | Maximum [Member]
Property, Plant and Equipment, Useful Life, Minimum	6 years
U.S. Pipe [Member] | Maximum [Member]
Discontinued Operations, Receivable from Buyer of Discontinued Operation	$ 3,500,000
Revolving Credit Facility [Member]
Debt Issuance Costs, Net	1,000,000
Secured Debt [Member]
Debt Issuance Costs, Net	5,300,000	$ 4,900,000
Unsecured Debt [Member]
Debt Issuance Costs, Net	$ 5,300,000

X

- Definition

Discontinued Operations, Receivable from Buyer of Discontinued Operation

+ References

No definition available.

+ Details

Name:	mwa_DiscontinuedOperationsReceivableFromBuyerOfDiscontinuedOperation
Namespace Prefix:	mwa_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Exposure to Workers Compensation Claims, Per Incident

+ References

No definition available.

+ Details

Name:	mwa_ExposureToWorkersCompensationClaimsPerIncident
Namespace Prefix:	mwa_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- Definition

Finite-Lived Tangible Asset Useful Life

+ References

No definition available.

+ Details

Name:	mwa_FiniteLivedTangibleAssetUsefulLife
Namespace Prefix:	mwa_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Income Tax Benefit, Likelihood of Realization Threshold

+ References

No definition available.

+ Details

Name:	mwa_IncomeTaxBenefitLikelihoodOfRealizationThreshold
Namespace Prefix:	mwa_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

X

- Definition

The carrying amount of a liability for an asset retirement obligation. An asset retirement obligation is a legal obligation associated with the disposal or retirement of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849

+ Details

Name:	us-gaap_AssetRetirementObligation
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- Definition

Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.17)
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1D
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495340-112611

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=124435984&loc=d3e28555-108399

+ Details

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

X

- Definition

The expense charged against earnings for the period pertaining to standard and extended warranties on the entity's goods and services granted to customers.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123570139&loc=d3e3602-108585

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
-SubTopic 10
-Section 50
-Paragraph 8
-Subparagraph ((c)(3,4))
-URI http://asc.fasb.org/extlink&oid=123368208&loc=d3e12565-110249

+ Details

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

X

- Definition

Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

+ References

No definition available.

+ Details

Name:	us-gaap_PropertyPlantAndEquipmentUsefulLife
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Carrying value as of the balance sheet date of obligations and payables pertaining to claims incurred of a workers compensation nature.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(15)(5))
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(15)(a))
-URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(20))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(24))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_WorkersCompensationLiabilityCurrentAndNoncurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_LandImprovementsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_BuildingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_MachineryAndEquipmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_SoftwareAndSoftwareDevelopmentCostsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis=mwa_UsPipeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DebtInstrumentAxis=us-gaap_RevolvingCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DebtInstrumentAxis=us-gaap_SecuredDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DebtInstrumentAxis=us-gaap_UnsecuredDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: