SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Short-Term Investments (Details) - USD ($)	12 Months Ended
Dec. 31, 2016	Dec. 31, 2015
Short-term investments
Short-term investments	$ 3,246,000	$ 0
Certificates of Deposit \| Minimum
Short-term investments
Maturity period	6 months
Certificates of Deposit \| Maximum
Short-term investments
Maturity period	12 months

Investments which are intended to be sold in the short term (usually less than one year or the normal operating cycle, whichever is longer) including trading securities, available-for-sale securities, held-to-maturity securities, and other short-term investments not otherwise listed in the existing taxonomy.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.2)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 03
-Paragraph 1
-Subparagraph g
-Article 7

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant