Inventories - Impairment of Inventory (Detail) - CNY (¥) ¥ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Provision of inventories [Abstract]
Beginning balance	¥ 221	¥ 226
Provision for inventories	20	12
Provision written off upon disposal	(187)	(17)
Ending balance	¥ 54	¥ 221

The amount of expense recognised related to the write-down of inventories to net realisable value. [Refer: Inventories]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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