Commitments and contingencies.

No definition available.

Name:	awk_CommitmentsAndContingenciesLineItems
Namespace Prefix:	awk_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Estimated capital expenditures under legal and binding contractual obligations.

+ References

No definition available.

+ Details

Name:	awk_EstimatedCapitalExpendituresUnderLegalAndBindingContractualObligations
Namespace Prefix:	awk_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Litigation Settlement, Amount Awarded from Other Party, Benefit To Customer, Regulatory Approval, Number Of Denied Applications

+ References

No definition available.

+ Details

Name:	awk_LitigationSettlementAmountAwardedFromOtherPartyBenefitToCustomerRegulatoryApprovalNumberOfDeniedApplications
Namespace Prefix:	awk_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Litigation Settlement, Amount Awarded from Other Party, Benefit To Customer, Regulatory Approval, Number Of Utility Subsidiaries

+ References

No definition available.

+ Details

Name:	awk_LitigationSettlementAmountAwardedFromOtherPartyBenefitToCustomerRegulatoryApprovalNumberOfUtilitySubsidiaries
Namespace Prefix:	awk_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Litigation Settlement, Amount Awarded From Other Party, Escrow

+ References

No definition available.

+ Details

Name:	awk_LitigationSettlementAmountAwardedFromOtherPartyEscrow
Namespace Prefix:	awk_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Litigation Settlement, Amount Awarded From Other Party, Escrow, Transfers

+ References

No definition available.

+ Details

Name:	awk_LitigationSettlementAmountAwardedFromOtherPartyEscrowTransfers
Namespace Prefix:	awk_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Loss Contingency Accrual, Net of Tax

+ References

No definition available.

+ Details

Name:	awk_LossContingencyAccrualNetOfTax
Namespace Prefix:	awk_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Loss Contingency, Cost Cap For Proposed Facilities

+ References

No definition available.

+ Details

Name:	awk_LossContingencyCostCapForProposedFacilities
Namespace Prefix:	awk_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Loss Contingency, Cost Cap For Proposed Facilities, Increase

+ References

No definition available.

+ Details

Name:	awk_LossContingencyCostCapForProposedFacilitiesIncrease
Namespace Prefix:	awk_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Loss Contingency, Estimate Of The Future Contribution

+ References

No definition available.

+ Details

Name:	awk_LossContingencyEstimateOfTheFutureContribution
Namespace Prefix:	awk_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Loss Contingency, Natural Gas Outage Inconvenience Per Household, Amount

+ References

No definition available.

+ Details

Name:	awk_LossContingencyNaturalGasOutageInconveniencePerHouseholdAmount
Namespace Prefix:	awk_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Loss Contingency, Natural Gas Outage Inconvenience Per Household, Average Amount Paid

+ References

No definition available.

+ Details

Name:	awk_LossContingencyNaturalGasOutageInconveniencePerHouseholdAverageAmountPaid
Namespace Prefix:	awk_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Loss Contingency, Number of Agreements

+ References

No definition available.

+ Details

Name:	awk_LossContingencyNumberOfAgreements
Namespace Prefix:	awk_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Loss Contingency, Number of Agreements, Valid

+ References

No definition available.

+ Details

Name:	awk_LossContingencyNumberOfAgreementsValid
Namespace Prefix:	awk_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Loss Contingency, Number of Agreements, Void

+ References

No definition available.

+ Details

Name:	awk_LossContingencyNumberOfAgreementsVoid
Namespace Prefix:	awk_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Loss Contingency, Number of Recommended Operational Improvements

+ References

No definition available.

+ Details

Name:	awk_LossContingencyNumberOfRecommendedOperationalImprovements
Namespace Prefix:	awk_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Loss Contingency, Pending Claims, Number of Answers Provided For

+ References

No definition available.

+ Details

Name:	awk_LossContingencyPendingClaimsNumberOfAnswersProvidedFor
Namespace Prefix:	awk_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Number of Customer Affected By Loss of Natural Gas Service

+ References

No definition available.

+ Details

Name:	awk_NumberOfCustomerAffectedByLossOfNaturalGasService
Namespace Prefix:	awk_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Number of Customer Serving

+ References

No definition available.

+ Details

Name:	awk_NumberOfCustomerServing
Namespace Prefix:	awk_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Number Of Customers For Whom A Precautionary Boil Water Advisory Was Issued To

+ References

No definition available.

+ Details

Name:	awk_NumberOfCustomersForWhomAPrecautionaryBoilWaterAdvisoryWasIssuedTo
Namespace Prefix:	awk_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Number of Customers Who Completed Claim Process

+ References

No definition available.

+ Details

Name:	awk_NumberOfCustomersWhoCompletedClaimProcess
Namespace Prefix:	awk_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Number of Focused General Investigations

+ References

No definition available.

+ Details

Name:	awk_NumberOfFocusedGeneralInvestigations
Namespace Prefix:	awk_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Potential Condemnation, Asset Value

+ References

No definition available.

+ Details

Name:	awk_PotentialCondemnationAssetValue
Namespace Prefix:	awk_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Potential Condemnation, Number of Statutory Standards Incorrectly Applied By Agency

+ References

No definition available.

+ Details

Name:	awk_PotentialCondemnationNumberOfStatutoryStandardsIncorrectlyAppliedByAgency
Namespace Prefix:	awk_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Potential Condemnation, Offer Rejection Amount

+ References

No definition available.

+ Details

Name:	awk_PotentialCondemnationOfferRejectionAmount
Namespace Prefix:	awk_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Potential Condemnation, Parcels of Land

+ References

No definition available.

+ Details

Name:	awk_PotentialCondemnationParcelsOfLand
Namespace Prefix:	awk_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Public Utilities, Allowance for Funds Used During Construction

+ References

No definition available.

+ Details

Name:	awk_PublicUtilitiesAllowanceForFundsUsedDuringConstruction
Namespace Prefix:	awk_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Public Utility, Aggregate Costs

+ References

No definition available.

+ Details

Name:	awk_PublicUtilityAggregateCosts
Namespace Prefix:	awk_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Public Utility, Approved Cost Estimates

+ References

No definition available.

+ Details

Name:	awk_PublicUtilityApprovedCostEstimates
Namespace Prefix:	awk_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Public Utility, Approved Recovery Amount

+ References

No definition available.

+ Details

Name:	awk_PublicUtilityApprovedRecoveryAmount
Namespace Prefix:	awk_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Public Utility, Daily Production, Number of Gallons Related to Desalinated Water

+ References

No definition available.

+ Details

Name:	awk_PublicUtilityDailyProductionNumberOfGallonsRelatedToDesalinatedWater
Namespace Prefix:	awk_
Data Type:	dtr-types:volumeItemType
Balance Type:	na
Period Type:	instant

- Definition

Public Utility, Initial Daily Production, Number of Gallons Related to Desalinated Water

+ References

No definition available.

+ Details

Name:	awk_PublicUtilityInitialDailyProductionNumberOfGallonsRelatedToDesalinatedWater
Namespace Prefix:	awk_
Data Type:	dtr-types:volumeItemType
Balance Type:	na
Period Type:	instant

- Definition

Area of a real estate property.

+ References

No definition available.

+ Details

Name:	us-gaap_AreaOfRealEstateProperty
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:areaItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount awarded from other party in judgment or settlement of litigation.

+ References

No definition available.

+ Details

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

- Definition

Amount awarded to other party in judgment or settlement of litigation.

+ References

No definition available.

+ Details

Name:	us-gaap_LitigationSettlementAmountAwardedToOtherParty
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of loss contingency liability.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 450
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483076/450-20-50-1

Reference 2: http://www.xbrl.org/2003/role/recommendedDisclosureRef
-Topic 450
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 10
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483076/450-20-50-10

+ Details

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

- Definition

Number of claims dismissed.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 450
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483076/450-20-50-4

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 450
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 9
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483076/450-20-50-9

+ Details

Name:	us-gaap_LossContingencyClaimsDismissedNumber
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Reflects the estimated amount of loss from the specified contingency as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 275
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 9
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482861/275-10-50-9

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 720
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483359/720-20-50-1

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Topic 460
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 27
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482395/460-10-55-27

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 450
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 9
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483076/450-20-50-9

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 450
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483076/450-20-50-4

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 460
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482425/460-10-50-3

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 460
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482425/460-10-50-2

+ Details

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

- Definition

Number of pending claims pertaining to a loss contingency.

+ References

+ Details

Name:	us-gaap_LossContingencyPendingClaimsNumber
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

The amount purchased during the period under an unrecorded unconditional purchase obligation (for example, under the take-or-pay or throughput contract).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 440
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482648/440-10-50-4

+ Details

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

- Details

Name:	dei_LegalEntityAxis=awk_CaliforniaAmericanWaterCompanyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementGeographicalAxis=awk_DunbarMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=awk_WestVirginiaAmericanWaterCompanyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementGeographicalAxis=stpr_WV
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RegulatoryAgencyAxis=awk_PublicServiceCommissionOfWestVirginiaMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=awk_MountaineerGasCompanyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=awk_MountaineerGasCompanyAndWestVirginiaAmericanWaterCompanyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementGeographicalAxis=awk_MontereyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RegulatoryAgencyAxis=awk_StateWaterResourcesControlBoardMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

Commitments and Contingencies - Additional Information (Details) gal in Millions			12 Months Ended
	Sep. 12, 2025 USD ($)	Apr. 24, 2024 claim	Dec. 31, 2025 USD ($) subsidiary state	Dec. 31, 2024 USD ($) customer	Dec. 31, 2023 USD ($)	Feb. 18, 2026 lawsuit	Oct. 09, 2025 a	Aug. 14, 2025 a	May 21, 2025 USD ($)	May 09, 2025 a	Jul. 24, 2024 improvement	Jun. 14, 2024 lawsuit	Dec. 20, 2023 lawsuit	Dec. 11, 2023 standard	Dec. 06, 2023 USD ($)	Nov. 16, 2023 investigation	Nov. 11, 2023 customer	Nov. 10, 2023 customer	Apr. 28, 2023 USD ($)	Dec. 05, 2022 USD ($)	Oct. 31, 2022 gal	Feb. 28, 2021 parcel	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 agreement
Commitments And Contingencies [Line Items]
Estimated capital expenditures under legal and binding contractual obligations			$ 1,500,000,000
Purchase obligation			138,000,000	$ 129,000,000	$ 125,000,000
Loss contingency, probable loss			8,000,000
Daily production, number of gallons related to desalinated water \| gal																					6.4
Initial daily production, number of gallons related to desalinated water \| gal																					4.8
Number of dismissed claims \| claim		1
Settlement payments received			$ 159,000,000
Number of utility subsidiaries \| subsidiary			7
Number of denied regulatory application \| state			2
Total escrow account funds held in law firm			$ 114,000,000
Escrowed funds			47,000,000
Cal Am
Commitments And Contingencies [Line Items]
Number of agreements, void \| agreement																										4
Number of agreements \| agreement																										5
Number of agreements, valid \| agreement																										1
Dunbar \| WVAWC
Commitments And Contingencies [Line Items]
Loss contingency, probable loss				5,000,000
Litigation settlement, proposed maximum pre-tax amount	$ 18,000,000
Litigation settlement, amount awarded to other party	$ 5,000,000
Loss contingency, probable loss, net of tax				$ 4,000,000
West Virginia \| WVPSC
Commitments And Contingencies [Line Items]
Number of focused general investigations \| investigation																2
West Virginia \| WVAWC
Commitments And Contingencies [Line Items]
Number of customers for whom a precautionary boil water advisory was issued to \| customer																	300
Number of customers who completed claim process \| customer				594
Natural gas outage inconvenience per household, average amount paid				$ 1,500
West Virginia \| Mountaineer Gas Company
Commitments And Contingencies [Line Items]
Number of customer serving (over) \| customer																		220,000
Number of customer affected by loss of natural gas service \| customer																		1,500
West Virginia \| Mountaineer Gas Company and WVAWC
Commitments And Contingencies [Line Items]
Number of pending lawsuits \| lawsuit												4
Number of pending lawsuits with answers provided for \| lawsuit													3
Number of recommended operational improvements \| improvement											3
West Virginia \| Mountaineer Gas Company and WVAWC \| Subsequent Event
Commitments And Contingencies [Line Items]
Number of pending lawsuits \| lawsuit						4
Monterey \| Cal Am
Commitments And Contingencies [Line Items]
Water supply projected area \| a							2,500	2,600		2,500
Potential condemnation, asset value																							$ 513,000,000
Potential condemnation, parcels of land \| parcel																						58
Potential condemnation, number of statutory standards incorrectly applied by agency \| standard														2
Potential condemnation, offer rejection amount																			$ 448,800,000
Monterey \| Cal Am \| SWRCB
Commitments And Contingencies [Line Items]
Approved cost estimates																								$ 279,000,000
Aggregate costs			324,000,000
Allowance for funds used during construction			107,000,000
Cost cap for proposed facilities, final																				$ 62,000,000
Cost cap for extraction wells									$ 11,000,000
Maximum
Commitments And Contingencies [Line Items]
Loss contingency, possible loss			$ 4,000,000
Maximum \| West Virginia \| WVAWC
Commitments And Contingencies [Line Items]
Natural gas outage inconvenience per household, amount															$ 2,000
Maximum \| Monterey \| Cal Am \| SWRCB
Commitments And Contingencies [Line Items]
Approved recovery amount																				$ 123,000,000					$ 50,000,000