XML 87 R71.htm IDEA: XBRL DOCUMENT v3.8.0.1

Retirement Plans (Accumulated and Projected Benefit Obligations) (Details) - USD ($) $ in Millions	Sep. 30, 2017	Sep. 30, 2016
Pension Plans with accumulated benefit obligations in excess of plan assets
Projected benefit obligation	$ 379.5	$ 402.0
Accumulated benefit obligation	379.5	402.0
Fair value of plan assets	364.2	337.9
Pension plans with plan assets in excess of accumulated benefit obligations
Projected benefit obligation	1.0	1.1
Accumulated benefit obligation	1.0	1.1
Fair value of plan assets	$ 2.1	$ 2.1

X

- Definition

Defined Benefit Plan, Pension Plans with Plan Assets in Excess of Accumulated Benefit Obligations [Abstract]

+ References

No definition available.

+ Details

Name:	mwa_DefinedBenefitPlanPensionPlansWithPlanAssetsInExcessOfAccumulatedBenefitObligationsAbstract
Namespace Prefix:	mwa_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Defined Benefit Plan, Pension Plans With Plan Assets In Excess Of Accumulated Benefit Obligations, Aggregate Accumulated Benefit Obligation

+ References

No definition available.

+ Details

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

X

- Definition

Defined Benefit Plan, Pension Plans With Plan Assets In Excess Of Accumulated Benefit Obligations, Aggregate Fair Value of Plan Assets

+ References

No definition available.

+ Details

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

X

- Definition

Defined Benefit Plan, Pension Plans With Plan Assets In Excess Of Accumulated Benefit Obligations, Aggregate Projected Benefit Obligation

+ References

No definition available.

+ Details

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

X

- References

No definition available.

+ Details

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

X

- Definition

Amount of accumulated benefit obligation for defined benefit pension plan with accumulated benefit obligation in excess of plan assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e2417-114920

+ Details

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

X

- Definition

Fair value of plan assets for defined benefit pension plan with accumulated benefit obligation in excess of plan assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e2417-114920

+ Details

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

X

- Definition

Amount of projected benefit obligation for defined benefit pension plan with accumulated benefit obligation in excess of plan assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 55
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=77993564&loc=d3e4179-114921

+ Details

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