INCOME TAXES - Net Operating Losses and Credit Carryforwards (Details) $ in Thousands	Dec. 31, 2018 USD ($)
Operating Loss Carryforwards [Line Items]
Carryforwards with unlimited carryforward period	$ 900
Federal
Operating Loss Carryforwards [Line Items]
Net operating losses	81,206
Credit carryforwards	7,480
Net operating losses expected to expire unused	60,200
Tax credits expected to expire unused	100
State
Operating Loss Carryforwards [Line Items]
Net operating losses	2,210
Credit carryforwards	1,937
Net operating losses expected to expire unused	800
Tax credits expected to expire unused	7,400
OpenSpan, Inc. | Federal
Operating Loss Carryforwards [Line Items]
Net operating losses	81,206
Credit carryforwards	640
OpenSpan, Inc. | State
Operating Loss Carryforwards [Line Items]
Net operating losses	665
Credit carryforwards	$ 324