Short-Term Investments - Schedule of Short-Term Investment (Details) ¥ in Thousands, $ in Thousands	Dec. 31, 2018 CNY (¥)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 CNY (¥)
Investments Debt And Equity Securities [Abstract]
Short-term investments	¥ 1,028,564	$ 149,598	¥ 353,070

Amount of investments including trading securities, available-for-sale securities, held-to-maturity securities, and short-term investments classified as other and current.

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Name:	us-gaap_ShortTermInvestments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant