SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Net Loss Per Share (Details) - shares shares in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Common shares not included in the computation of diluted net loss per share
Potentially issuable common shares not included in the computation of diluted net loss per share because they would have an anti-dilutive effect	10,206	11,069
Stock Options
Common shares not included in the computation of diluted net loss per share
Potentially issuable common shares not included in the computation of diluted net loss per share because they would have an anti-dilutive effect	4,042	5,080
Restricted Stock Awards
Common shares not included in the computation of diluted net loss per share
Potentially issuable common shares not included in the computation of diluted net loss per share because they would have an anti-dilutive effect	6,164	5,989