Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) $ in Millions |
Sep. 30, 2020 |
Dec. 31, 2019 |
|---|---|---|
| Statement of Financial Position [Abstract] | ||
| Allowance for uncollectible accounts | $ 52 | $ 41 |
| Common stock, par value (dollars per share) | $ 0.01 | $ 0.01 |
| Common stock, shares authorized (in shares) | 500,000,000 | 500,000,000 |
| Common stock, shares issued (in shares) | 186,437,589 | 185,903,727 |
| Treasury Stock, shares (in shares) | 5,168,086 | 5,090,855 |