INCOME TAXES (Summary of Valuation Allowance) (Details) - CNY (¥)
¥ in Thousands
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Balance at the beginning of the year ¥ 26,507 ¥ 20,115 ¥ 14,362
Additions of valuation allowance 15,868 13,076 9,069
Reduction of valuation allowance (5,429) (6,684) (3,316)
Balance at the end of the year ¥ 36,946 ¥ 26,507 ¥ 20,115