Related Party Transactions - Balances with Related Parties (Parenthetical) (Detail) ¥ in Thousands, $ in Thousands |
Dec. 31, 2017
CNY (¥)
|
Dec. 31, 2017
USD ($)
|
Dec. 31, 2016
CNY (¥)
|
|---|---|---|---|
| Ping An Group [Member] | |||
| Related Party Transaction [Line Items] | |||
| Cash and cash equivalents and short term investments | ¥ 1,374,574 | $ 211,268 | ¥ 541,218 |