Long-Term Debt - Issued (Details) - USD ($) $ in Millions |
6 Months Ended | |
|---|---|---|
Jun. 30, 2018 |
Jun. 30, 2017 |
|
| Debt Instrument [Line Items] | ||
| Total issuances | $ 15 | $ 20 |
| Other American Water subsidiaries | Private activity bonds and government funded debt | Fixed rate | ||
| Debt Instrument [Line Items] | ||
| Total issuances | $ 15 | |
| Other American Water subsidiaries | Private activity bonds and government funded debt | Minimum | Fixed rate | ||
| Debt Instrument [Line Items] | ||
| Interest rate | 0.00% | |
| Maturity date | 2021 | |
| Other American Water subsidiaries | Private activity bonds and government funded debt | Maximum | Fixed rate | ||
| Debt Instrument [Line Items] | ||
| Interest rate | 5.00% | |
| Maturity date | 2048 | |
| New Jersey Environmental Infrastructure Financing Program | ||
| Debt Instrument [Line Items] | ||
| Total issuances | $ 14 | |