Public Utilities, Adjustment, Common Equity Ratio Percentage

No definition available.

Name:	awk_PublicUtilitiesAdjustmentCommonEquityRatioPercentage
Namespace Prefix:	awk_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Public Utilities, Authorized Rate Base, Amount

+ References

No definition available.

+ Details

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

- Definition

Public Utilities, Authorized Rate Base Not Included In General Rate Case Order, Amount

+ References

No definition available.

+ Details

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

- Definition

Public Utilities, Common Equity Ratio Percentage

+ References

No definition available.

+ Details

Name:	awk_PublicUtilitiesCommonEquityRatioPercentage
Namespace Prefix:	awk_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Public Utilities, Debt Ratio Percentage

+ References

No definition available.

+ Details

Name:	awk_PublicUtilitiesDebtRatioPercentage
Namespace Prefix:	awk_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Public Utilities, General Rate Case Authorizations, Annualized Incremental Revenues, Approved Amount

+ References

No definition available.

+ Details

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

- Definition

Public Utilities, General Rate Case Authorizations, Annualized Incremental Revenues, Approved Amount, Increase (Decrease) In Capital Investments

+ References

No definition available.

+ Details

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

- Definition

Public Utilities, General Rate Case Authorizations, Annualized Incremental Revenues, Estimated and Not Approved Amount

+ References

No definition available.

+ Details

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

- Definition

Public Utilities, General Rate Case Authorizations, Annualized Incremental Revenues, Previously Approved Infrastructure Filings Amount

+ References

No definition available.

+ Details

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

- Definition

Public Utilities, General Rate Case Authorizations, Annualized Incremental Revenues, Requested Rate, Increase (Decrease) In Capital Investments

+ References

No definition available.

+ Details

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

- Definition

Percentage of public utility's approved return on equity.

+ References

No definition available.

+ Details

Name:	us-gaap_PublicUtilitiesApprovedReturnOnEquityPercentage
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
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

No definition available.

+ Details

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

- Details

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

- Details

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

- Details

Name:	awk_PublicUtilityAuthorizationEffectiveDateAxis=awk_PublicUtilityAuthorizationEffectiveDateFebruary262026Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	awk_PublicUtilityAuthorizationEffectiveDateAxis=awk_PublicUtilityAuthorizationEffectiveDateYear2024Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	awk_PublicUtilityAuthorizationEffectiveDateAxis=awk_PublicUtilityAuthorizationEffectiveDateYear2025Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	awk_PublicUtilityAuthorizationEffectiveDateAxis=awk_PublicUtilityAuthorizationEffectiveDateYear2026Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Regulatory Matters - General Rate Cases Additional Information (Details) - USD ($) $ in Millions	Jul. 27, 2026	Jun. 08, 2026	Mar. 05, 2026	Feb. 26, 2026	Dec. 05, 2024
Pennsylvania \| Subsequent Event
Public Utilities, General Disclosures
General rate case authorizations, annualized incremental revenues, approved amount	$ 75
General rate case authorizations, annualized incremental revenues, previously approved infrastructure filings amount	$ 24
Authorized return on equity, percentage	9.55%
Common equity, adjustment, percentage	54.23%
Debt ratio, percentage	45.77%
Authorized rate base amount	$ 6,600
General rate case authorizations, annualized incremental revenues, approved amount, increase in capital investments	$ 1,200
West Virginia
Public Utilities, General Disclosures
General rate case authorizations, annualized incremental revenues, approved amount			$ 20
General rate case authorizations, annualized incremental revenues, previously approved infrastructure filings amount			$ 13
Authorized return on equity, percentage			9.80%
Common equity, adjustment, percentage			51.00%
Debt ratio, percentage			49.00%
General rate case authorizations, annualized incremental revenues, approved amount, increase in capital investments			$ 239
Public utilities, authorized rate base not included in general rate case order, amount			$ 1,100
Maryland
Public Utilities, General Disclosures
General rate case authorizations, annualized incremental revenues, approved amount				$ 2
Authorized return on equity, percentage				9.75%
Debt ratio, percentage				47.68%
Common equity, percentage				52.32%
General rate case authorizations, annualized incremental revenues, requested rate, increase in capital investments				$ 22
Maryland \| Year 2026
Public Utilities, General Disclosures
General rate case authorizations, annualized incremental revenues, approved amount				$ 1
California
Public Utilities, General Disclosures
Authorized return on equity, percentage					10.20%
General rate case authorizations, annualized incremental revenues, requested rate, increase in capital investments		$ 750
California \| Year 2024
Public Utilities, General Disclosures
General rate case authorizations, annualized incremental revenues, approved amount					$ 21
California \| Year 2025
Public Utilities, General Disclosures
General rate case authorizations, annualized incremental revenues, estimated and not approved amount					16
California \| Year 2026
Public Utilities, General Disclosures
General rate case authorizations, annualized incremental revenues, estimated and not approved amount					$ 16