Contractual interest rate for funds borrowed, under the debt agreement.

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-Name Accounting Standards Codification
-Topic 230
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Long-Term Debt - Issued (Details) - USD ($) $ in Millions	12 Months Ended
Long-Term Debt - Issued (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Total issuances	$ 822	$ 1,118	$ 1,334
Other American Water subsidiaries \| Private activity bonds and government funded debt \| Fixed rate
Debt Instrument [Line Items]
Total issuances	$ 22
Other American Water subsidiaries \| Private activity bonds and government funded debt \| Fixed rate \| Minimum
Debt Instrument [Line Items]
Rate	0.00%
Other American Water subsidiaries \| Private activity bonds and government funded debt \| Fixed rate \| Maximum
Debt Instrument [Line Items]
Rate	1.75%
Other American Water subsidiaries \| Private activity bonds and government funded debt \| Fixed rate \| Weighted Average
Debt Instrument [Line Items]
Rate	1.03%
American Water Capital Corp. (AWCC) \| Senior notes \| Fixed rate
Debt Instrument [Line Items]
Total issuances	$ 800
American Water Capital Corp. (AWCC) \| Senior notes \| Fixed rate \| Minimum
Debt Instrument [Line Items]
Rate	4.45%
American Water Capital Corp. (AWCC) \| Senior notes \| Fixed rate \| Weighted Average
Debt Instrument [Line Items]
Rate	4.45%