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Related Party Transactions - Additional Information (Detail)
¥ in Millions, $ in Millions
12 Months Ended
Dec. 31, 2017
USD ($)
Dec. 31, 2017
CNY (¥)
Dec. 31, 2016
CNY (¥)
Dec. 31, 2015
CNY (¥)
Ctrip.com International, Ltd        
Related Party Transaction [Line Items]        
Related party transactions $ 115 ¥ 750 ¥ 631 ¥ 89