Earnings Per Share - Additional Information (Details) - shares shares in Millions |
3 Months Ended | |
|---|---|---|
Mar. 31, 2018 |
Mar. 31, 2017 |
|
| Stock option awards | ||
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||
| Anti-diluted shares excluded from computation of earnings per share (in shares) | 0.2 | 4.1 |
| Common Stock Class C | Common Stock | ||
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||
| Anti-diluted shares excluded from computation of earnings per share (in shares) | 14.7 | 19.1 |