Short-Term Debt - Additional Information (Details)
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12 Months Ended |
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|
Dec. 31, 2019
USD ($)
Extension
|
Dec. 31, 2018
USD ($)
|
Mar. 21, 2018
USD ($)
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| Short-term Debt [Line Items] |
|
|
|
| Short-term debt |
$ 786,000,000
|
$ 964,000,000
|
|
| Maturity in More Than Three Months |
|
|
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| Short-term Debt [Line Items] |
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|
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| Proceeds from short-term borrowings with maturities greater than three months |
0
|
|
|
| Letter of Credit |
|
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| Short-term Debt [Line Items] |
|
|
|
| Available credit facility capacity |
2,170,000,000
|
|
|
| Commercial Paper Program |
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| Short-term Debt [Line Items] |
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|
|
| Short-term debt |
786,000,000
|
964,000,000
|
|
| Revolving Credit Facility |
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|
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| Short-term Debt [Line Items] |
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|
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| Maximum borrowing capacity |
2,250,000,000
|
2,262,000,000
|
|
| Letters of credit, outstanding amount |
76,000,000
|
|
|
| Revolving Credit Facility | Letter of Credit |
|
|
|
| Short-term Debt [Line Items] |
|
|
|
| Maximum borrowing capacity |
$ 150,000,000
|
$ 150,000,000
|
|
| American Water Capital Corp. |
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|
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| Short-term Debt [Line Items] |
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|
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| Interest rate during period |
2.54%
|
2.28%
|
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| Maximum borrowing capacity |
|
|
$ 500,000,000
|
| Number of extensions allowed | Extension |
2
|
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| Extension period duration |
1 year
|
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| American Water Capital Corp. | Revolving Credit Facility |
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| Short-term Debt [Line Items] |
|
|
|
| Proceeds from lines of credit |
$ 0
|
|
|
| American Water Capital Corp. | Revolving Credit Facility | Letter of Credit |
|
|
|
| Short-term Debt [Line Items] |
|
|
|
| Maximum borrowing capacity |
|
|
$ 150,000,000
|