Accounts Receivable, Net - Schedule of Analysis of Allowance for Doubtful Accounts (Detail)
¥ in Thousands, $ in Thousands
12 Months Ended
Dec. 31, 2017
CNY (¥)
Dec. 31, 2017
USD ($)
Dec. 31, 2016
CNY (¥)
Receivables [Abstract]      
Beginning balance ¥ 512 $ 79 ¥ 2,315
Additions charged to bad debt expense 1,854 284 2,792
Reversal (744) (114) (489)
Write off (214) (33) (4,106)
Ending balance ¥ 1,408 $ 216 ¥ 512