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Treasury Stock - Additional Information (Detail) ¥ in Thousands		12 Months Ended
	Mar. 16, 2016 USD ($)	Dec. 31, 2016 CNY (¥) shares
Equity, Class of Treasury Stock [Line Items]
Payments for Repurchase of Common Stock | ¥		¥ 178,991
Share Repurchase Plan
Equity, Class of Treasury Stock [Line Items]
Stock repurchase program, authorized amount | $	$ 100,000,000
Stock Repurchase Program, Period in Force	1 year
Payments for Repurchase of Common Stock | ¥		¥ 178,991
Share Repurchase Plan | Common Class A [Member]
Equity, Class of Treasury Stock [Line Items]
Repurchase of common stock | shares		25,368,080
Share Repurchase Plan | ADS
Equity, Class of Treasury Stock [Line Items]
Repurchase of common stock | shares		2,536,808

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The cash outflow to reacquire common stock during the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3291-108585

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Amount of stock repurchase plan authorized.

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Period which shares may be purchased under a stock repurchase plan authorized by an entity's Board of Directors, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(29))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 2
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