Summary of significant accounting policies (Narrative) (Details)	12 Months Ended
Dec. 31, 2015 USD ($)	Dec. 31, 2015 CNY (¥)	Dec. 31, 2014 CNY (¥)	Dec. 31, 2013 CNY (¥)
RMB to USD exchange rate used in translation	6.4778	6.4778
Impairment loss from cost method investment			¥ 3,029,000
Advertising and market promotion expenses		¥ 159,153,000	97,576,000	¥ 27,905,000
Employee social security and welfare benefits included as expenses		¥ 18,291,000	¥ 12,174,000	¥ 3,125,000
Goodwill impairment loss

This item represents an other than temporary decline in value that has been recognized against an investment accounted for under the cost method of accounting. The excess of the carrying amount over the fair value of the investment represents the amount of the write down which is or was reflected in earnings. The written down value is a new cost basis with the adjusted value of the investment becoming its new carrying value. Evidence of a loss in value might include, but would not necessarily be limited to, absence of an ability to recover the carrying amount of the investment or inability of the investee to sustain an earnings capacity which would justify the carrying amount of the investment.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 325
-SubTopic 20
-Section 50
-Paragraph 1
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- Definition

Foreign exchange rate used to translate amounts denominated in functional currency to reporting currency.

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- Definition

Amount of loss from the write-down of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

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- Definition

The total expense recognized in the period for promotion, public relations, and brand or product advertising.

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-Name Accounting Standards Codification
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- Definition

The amount of pension and other (such as medical, dental and life insurance) postretirement benefit costs recognized during the period for (1) defined benefit plans (periodic benefit costs include the following components: service cost, interest cost, expected return on plan assets, gain (loss) on assets, prior service cost or credit, transition asset or obligation, and gain (loss) due to settlements or curtailments) and for (2) defined contribution plans (to the extent that a plan's defined contributions to an individual's account are to be made for periods in which that individual renders services, the net cost for a period is the contribution called for in that period; if a plan calls for contributions for periods after an individual retires or terminates, the estimated cost is accrued during the employee's service period).

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