Prepaid Expenses and Other Current Assets - Additional Information (Detail) ¥ in Thousands, $ in Thousands |
Dec. 31, 2017
CNY (¥)
|
Dec. 31, 2017
USD ($)
|
Dec. 31, 2016
CNY (¥)
|
|---|---|---|---|
| Prepaid Expenses And Other Current Assets [Line Items] | |||
| Prepaid purchase cost | ¥ 125,317 | $ 19,262 | ¥ 317,262 |
| Motor Vehicles [Member] | |||
| Prepaid Expenses And Other Current Assets [Line Items] | |||
| Prepaid purchase cost | ¥ 226,419 |