XML 48 R37.htm IDEA: XBRL DOCUMENT v3.3.1.900

Commitments and Contingencies (Details) CAD in Millions, $ in Millions	3 Months Ended
	Dec. 31, 2015 USD ($)	Dec. 31, 2015 CAD	Dec. 31, 2014 USD ($)
Loss Contingency, Damages Sought, Value | CAD		CAD 10.0
Amount payable pending completion of an IRS audit	$ 11.6
Operating Leases
Proceeds from Sale of Productive Assets	0.0		$ 3.6
Prior To 1995 [member]
Walter Energy tax assessment			$ 33.0
IRS-Walter Energy Claim 1 [Member]
Loss Contingency, Range of Possible Loss, Maximum	554.3
IRS-Walter Energy Claim 1 Priority [Member]
Loss Contingency, Range of Possible Loss, Maximum	229.1
IRS-Walter Energy Claim 2 [Member]
Loss Contingency, Range of Possible Loss, Maximum	860.4
IRS-Walter Energy Claim 2 Priority [Member]
Loss Contingency, Range of Possible Loss, Maximum	$ 535.3

X

- Definition

Total amount of tax claimed for issues at a former affiliate.

+ References

No definition available.

+ Details

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

X

- Definition

The receivable from a former affiliate expected to be collected after their final settlement with a taxing authority.

+ References

No definition available.

+ Details

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

X

- References

No definition available.

+ Details

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

X

- Definition

The value (monetary amount) of the award the plaintiff seeks in the legal matter.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14326-108349

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 9
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14557-108349

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14435-108349

+ Details

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

X

- Definition

The estimated maximum amount of possible loss from the contingency.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14435-108349

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 9
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14557-108349

+ Details

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

X

- Definition

The cash inflow from the sale of property, plant and equipment (capital expenditures), software, and other intangible assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 12
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=56944662&loc=d3e3179-108585

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Investing Activities
-URI http://asc.fasb.org/extlink&oid=6516133

+ Details

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

X

- Details

Name:	mwa_CommitmentsAndContingenciesTimeFrameAxis=mwa_PriorTo1995Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	mwa_ClaimPriorityAxis=mwa_IRSWalterEnergyClaim1TotalMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	mwa_ClaimPriorityAxis=mwa_IRSWalterEnergyClaim1PriorityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	mwa_ClaimPriorityAxis=mwa_IRSWalterEnergyClaim2Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	mwa_ClaimPriorityAxis=mwa_IRSWalterEnergyClaim2PriorityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: