Restricted net assets (Details) ¥ in Millions	12 Months Ended
Mar. 31, 2017 CNY (¥)
Restricted net assets
Percentage of net income from subsidiaries and consolidated VIEs incorporated in the PRC to be appropriated to the statutory reserve	10.00%
Limit of statutory reserve fund as a percentage of registered capital, after which allocations to statutory reserve fund are no longer required	50.00%
Restricted net assets	¥ 45,472

Amount of restricted net assets of consolidated and unconsolidated subsidiaries as of the end of the most recently completed fiscal year.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(e)(3)(ii))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

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