Consolidated Balance Sheets (Unaudited) (Parenthetical) - $ / shares |
Mar. 31, 2018 |
Dec. 31, 2017 |
|---|---|---|
| Statement of Financial Position [Abstract] | ||
| 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) | 182,723,455 | 182,508,564 |
| Treasury Stock, shares (in shares) | 4,682,156 | 4,064,010 |