SEGMENT INFORMATION - SEGMENT RESULTS (Details) ¥ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2019 CNY (¥)	Dec. 31, 2019 USD ($)	[1]	Dec. 31, 2018 CNY (¥)	Dec. 31, 2017 CNY (¥)
Segment revenue
Total revenue	¥ 21,178,351	$ 3,042,080		¥ 19,828,018	¥ 18,331,422
Segment result	1,009,092	144,948		1,068,800	1,347,132
Finance costs - net	56,710	8,146		630	10,170
Share of results of associates, net of tax	(7,039)	(1,011)		7,177	6,944
Depreciation of fixed assets	1,637,298			1,609,743	1,662,460
Depreciation of righ-of-use assets	65,324
Amortization of leasehold land payments	0			55,782	45,680
Amortization of long-term prepaid expenses	16,438			12,909	3,168
Impairment of fixed assets	20,697			10,364	11,185
Provision for impairment of materials and supplies	10,793			11,361	7,844
Overtime [member]
Segment revenue
Total revenue	20,880,326			19,521,782	18,014,774
At a point in time
Segment revenue
Total revenue	298,025			306,236	316,648
Eliminations [member]
Segment revenue
Total revenue	(56,735)			(48,354)	(64,563)
Segment result	0			(25,270)	(8,988)
Eliminations [member] | Overtime [member]
Segment revenue
Total revenue	(56,735)			(48,354)	(64,563)
Eliminations [member] | At a point in time
Segment revenue
Total revenue	0			0	0
The Railway Transportation Business [member]
Segment revenue
Total revenue	20,963,634			19,603,098	18,000,324
Segment result	1,045,581			1,120,148	1,341,601
Finance costs - net	56,439			451	10,011
Share of results of associates, net of tax	(7,039)			7,177	6,944
Depreciation of fixed assets	1,633,185			1,603,106	1,655,657
Depreciation of righ-of-use assets	53,992			0	0
Amortization of leasehold land payments	0			44,450	34,348
Amortization of long-term prepaid expenses	16,008			12,596	3,256
Impairment of fixed assets	20,697			10,364	11,185
Provision for impairment of materials and supplies	10,793			11,361	7,844
The Railway Transportation Business [member] | Overtime [member]
Segment revenue
Total revenue	20,826,847			19,480,546	17,899,006
The Railway Transportation Business [member] | At a point in time
Segment revenue
Total revenue	136,787			122,552	101,318
All other segments [member]
Segment revenue
Total revenue	271,452			273,274	395,661
Segment result	(36,489)			(26,078)	14,519
Finance costs - net	271			179	159
Share of results of associates, net of tax	0			0	0
Depreciation of fixed assets	4,113			6,637	6,803
Depreciation of righ-of-use assets	11,332			0	0
Amortization of leasehold land payments	0			11,332	11,332
Amortization of long-term prepaid expenses	430			313	(88)
Impairment of fixed assets	0			0	0
Provision for impairment of materials and supplies	0			0	0
All other segments [member] | Overtime [member]
Segment revenue
Total revenue	110,214			89,590	180,331
All other segments [member] | At a point in time
Segment revenue
Total revenue	161,238			183,684	215,330
Railroad Businesses [member]
Segment revenue
Total revenue	20,025,568	2,876,493		18,823,379	17,294,901
Depreciation of fixed assets	1,612,683	231,647		1,581,685	1,632,926
Depreciation of righ-of-use assets	53,992	7,755
Amortization of leasehold land payments				44,450	34,348
Railroad Businesses [member] | Eliminations [member]
Segment revenue
Total revenue	0			0	0
Railroad Businesses [member] | The Railway Transportation Business [member]
Segment revenue
Total revenue	20,025,568			18,823,379	17,294,901
Railroad Businesses [member] | All other segments [member]
Segment revenue
Total revenue	0			0	0
Other Businesses [member]
Segment revenue
Total revenue	1,152,783	165,587		1,004,639	1,036,521
Depreciation of fixed assets	24,615	3,536		28,058	29,534
Depreciation of righ-of-use assets	11,332	$ 1,628
Amortization of leasehold land payments				11,332	11,332
Other Businesses [member] | Eliminations [member]
Segment revenue
Total revenue	(56,735)			(48,354)	(64,563)
Other Businesses [member] | The Railway Transportation Business [member]
Segment revenue
Total revenue	938,066			779,719	705,423
Other Businesses [member] | All other segments [member]
Segment revenue
Total revenue	¥ 271,452			¥ 273,274	¥ 395,661

[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.