Significant Accounting Policies - Additional Information (Details) - USD ($) $ in Millions |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2019 |
Dec. 31, 2018 |
Dec. 31, 2017 |
|
| Significant Accounting Policies [Line Items] | |||
| Estimated refunds | $ 25 | $ 23 | |
| Amortization of contributions in aid of construction | $ 29 | 28 | $ 27 |
| Payment terms from billing, period | 30 days | ||
| Payments for environmental loss contingencies | $ 1 | ||
| Remediation costs accrued | 2 | 4 | |
| Software | |||
| Significant Accounting Policies [Line Items] | |||
| Acquisition cost, carrying value | $ 345 | $ 336 | |
| Market-Based Businesses | |||
| Significant Accounting Policies [Line Items] | |||
| Payment terms from billing, period | 12 months | ||
| Maximum | |||
| Significant Accounting Policies [Line Items] | |||
| Payment terms from billing, period | 1 year | ||