Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - $ / shares |
Mar. 31, 2018 |
Dec. 31, 2017 |
|---|---|---|
| Statement of Financial Position [Abstract] | ||
| Par value (in dollars per share) | $ 1 | $ 1 |
| Shares authorized (in shares) | 100,000,000 | 100,000,000 |
| Shares issued (in shares) | 50,900,000 | 50,500,000 |
| Shares outstanding (in shares) | 50,900,000 | 50,500,000 |