INVESTMENTS IN JOINT VENTURES AND ASSOCIATES - Joint ventures (Details) ¥ in Thousands, $ in Thousands	12 Months Ended
Dec. 31, 2020 USD ($)	Dec. 31, 2020 CNY (¥)	Dec. 31, 2019 CNY (¥)	Dec. 31, 2018 CNY (¥)
INVESTMENTS IN JOINT VENTURES AND ASSOCIATES
As at January 1		¥ 3,385,582	¥ 3,393,349
Share of profits and losses for the year	$ 27,663	180,502	270,115	¥ (199,452)
Share of changes in reserves		3,046	(7,811)
Cash dividends declared		(480,397)	(50,314)
As at December 31	$ 517,173	3,374,553	3,385,582	3,393,349
Joint venture
INVESTMENTS IN JOINT VENTURES AND ASSOCIATES
As at January 1		3,385,582	3,393,349
Capital injections		4,333	50,000
Disposal			(114,604)
Share of profits and losses for the year		180,502	270,115
Share of changes in reserves		1,491	8,746
Cash dividends declared		(197,355)	(222,024)
As at December 31		3,374,553	3,385,582	¥ 3,393,349
Guangxi Huayin Aluminum Co., Ltd.
INVESTMENTS IN JOINT VENTURES AND ASSOCIATES
As at January 1		1,403,117
As at December 31		1,477,162	¥ 1,403,117
Registered and paid-in capital		¥ 2,441,987
Ownership interest in joint venture (as a percent)	33.00%	33.00%	33.00%
Voting power in joint venture (as a percent)	33.00%	33.00%
Profit sharing in joint venture (as a percent)	33.00%	33.00%

The increase in associates and joint ventures resulting from capital injections.

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Represents the decrease in investment in joint venture due to disposal.

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No definition available.

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The increase (decrease) in associates and joint ventures resulting from changes that the entity does not separately disclose in the same statement or note.

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No definition available.

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Investments in joint ventures accounted for using equity method, registered and paid-in capital

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No definition available.

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The proportion of profit sharing percentage in a joint venture attributable to the entity.

+ References

No definition available.

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Line items represent concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes of the table.

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No definition available.

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The amount of dividends that the company has declared but not yet paid.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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The amount of investments in joint ventures accounted for using the equity method. [Refer: Joint ventures [member]; Investments accounted for using equity method]

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The proportion of ownership interest in a joint venture attributable to the entity. [Refer: Joint ventures [member]]

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The proportion of the voting rights in a joint venture held by the entity. [Refer: Joint ventures [member]]

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The entity's share of the profit (loss) of joint ventures accounted for using the equity method. [Refer: Investments accounted for using equity method; Joint ventures [member]; Profit (loss)]

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