ORGANIZATION, BASIS OF PRESENTATION AND ACCOUNTING POLICIES - Liquidity (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016	Dec. 31, 2015
ORGANIZATION, BASIS OF PRESENTATION AND ACCOUNTING POLICIES
Cash and cash equivalents	$ 55,776	$ 93,032	$ 55,776	$ 93,032	$ 64,943	$ 24,816
Substantial doubt regarding sufficient funds in next twelve months			false
Net loss	$ (27,520)	$ (17,475)	$ (54,997)	$ (51,263)	$ (103,000)