INVESTMENTS IN ASSOCIATES - SUMMARISED BALANCE SHEETS (Details) ¥ in Thousands, $ in Thousands	Dec. 31, 2019 CNY (¥)	Dec. 31, 2019 USD ($)	[1]	Dec. 31, 2018 CNY (¥)	Dec. 31, 2017 CNY (¥)	Dec. 31, 2016 CNY (¥)
Disclosure of associates [line items]
Current assets	¥ 6,703,937	$ 962,961		¥ 6,356,677
Non-current assets	30,189,196	4,336,406		29,045,560
Total assets	36,893,133	5,299,367		35,402,237
Current liabilities	6,477,044	930,370		6,422,245
Equity	29,139,281	$ 4,185,596		28,816,329	¥ 28,607,408	¥ 28,030,055
Share of net assets	174,686			181,725
Guangzhou Tiecheng Enterprise Company Limited ("Tiecheng") [member]
Disclosure of associates [line items]
Current assets	77,732			121,465
Non-current assets	361,864			326,644
Total assets	439,596			448,109
Current liabilities	223,295			208,458
Equity	216,301			239,651
Share of net assets	105,987			117,429
Carrying amount of interest in associates	105,987			117,429	112,020
Shenzhen Guangzhou Railway Civil Engineering Company ("Shentu") [member]
Disclosure of associates [line items]
Current assets	1,612,909			1,143,125
Non-current assets	12,941			12,794
Total assets	1,625,850			1,155,919
Current liabilities	1,485,647			1,024,702
Equity	140,203			131,217
Share of net assets	68,699			64,296
Carrying amount of interest in associates	¥ 68,699			¥ 64,296	¥ 62,528

[1] Translation of amounts from Renminbi ("RMB") into United States dollars ("US$") for the convenience of the reader has been made at US$1.00=RMB6.9618, the certified exchange rates for December 31, 2019 as published by the Federal Reserve Board of the United States. No representation is made that the RMB amounts could have been, or could be, converted into US$ at that rate on December 31, 2019 or on any other date.