Earnings (Loss) per Share - Additional Information (Detail) - shares |
3 Months Ended | 6 Months Ended | |
|---|---|---|---|
Jun. 30, 2018 |
Jun. 30, 2017 |
Jun. 30, 2018 |
|
| Common Stock [Member] | Exchangeable Notes [Member] | |||
| Class of Stock [Line Items] | |||
| Conversion of exchangeable notes excluded from computation of diluted earnings per share | 10,448,213 | 10,448,213 | 10,448,213 |