COMMITMENTS AND CONTINGENCIES - Contingencies (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
COMMITMENTS AND CONTINGENCIES
Net revenues generated from these kindergartens	$ 140,803	$ 108,513	$ 82,858
VIE's Kindergartens
COMMITMENTS AND CONTINGENCIES
Net revenues generated from these kindergartens	$ 7,241	$ 4,489	$ 2,358

Total revenue from sale of goods and services rendered during the reporting period, in the normal course of business, reduced by sales returns and allowances, and sales discounts.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.1)
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

Name:	us-gaap_SalesRevenueNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration