Consolidated Balance Sheets (Parenthetical) - $ / shares shares in Millions |
Dec. 31, 2019 |
Dec. 31, 2018 |
|---|---|---|
| Stockholders' equity: | ||
| Common stock, shares authorized (in shares) | 500.0 | 500.0 |
| Common stock, par value (in dollars per share) | $ 0.001 | $ 0.001 |
| Common stock, shares issued (in shares) | 90.6 | 90.6 |
| Treasury stock (in shares) | 35.0 | 35.2 |