Recent accounting pronouncements (Details) - ASU 2015-17 - Reclassified - CNY (¥) ¥ in Millions	Mar. 31, 2017	Mar. 31, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Current deferred tax assets	¥ 652	¥ 451
Non-current deferred tax assets	652	451
Current deferred tax liabilities	207	9
Non-current deferred tax liabilities	¥ 207	¥ 9

Amount after allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences and carryforwards classified as current.

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Amount after allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences and carryforwards classified as noncurrent.

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Gross amount of noncurrent deferred tax liabilities, which result from applying the applicable tax rate to taxable temporary differences pertaining to each jurisdiction to which the entity is obligated to pay income tax.

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