CASH, CASH EQUIVALENTS AND SHORT-TERM INVESTMENTS - Schedule of Fair Value Hierarchy for Financial Assets and Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017	Nov. 30, 2017
Lazanda
Liabilities:
Contingent consideration			$ 200
Recurring
Assets:
Total	$ 15,202	$ 24,970
Liabilities:
Total	877	1,613
Recurring | Zipsor
Liabilities:
Contingent consideration	367	464
Recurring | Lazanda
Liabilities:
Contingent consideration		156
Recurring | CAMBIA
Liabilities:
Contingent consideration	510	993
Recurring | Corporate debt securities
Assets:
Total		1,205
Recurring | Money market funds
Assets:
Total	13	95
Recurring | Commercial paper
Assets:
Total	15,189	23,670
Recurring | Level 1
Assets:
Total	13	95
Liabilities:
Total	0	0
Recurring | Level 1 | Zipsor
Liabilities:
Contingent consideration	0	0
Recurring | Level 1 | Lazanda
Liabilities:
Contingent consideration		0
Recurring | Level 1 | CAMBIA
Liabilities:
Contingent consideration	0	0
Recurring | Level 1 | Corporate debt securities
Assets:
Total		0
Recurring | Level 1 | Money market funds
Assets:
Total	13	95
Recurring | Level 1 | Commercial paper
Assets:
Total	0	0
Recurring | Level 2
Assets:
Total	15,189	24,875
Liabilities:
Total	0	0
Recurring | Level 2 | Zipsor
Liabilities:
Contingent consideration	0	0
Recurring | Level 2 | Lazanda
Liabilities:
Contingent consideration		0
Recurring | Level 2 | CAMBIA
Liabilities:
Contingent consideration	0	0
Recurring | Level 2 | Corporate debt securities
Assets:
Total		1,205
Recurring | Level 2 | Money market funds
Assets:
Total	0	0
Recurring | Level 2 | Commercial paper
Assets:
Total	15,189	23,670
Recurring | Level 3
Assets:
Total	0	0
Liabilities:
Total	877	1,613
Recurring | Level 3 | Zipsor
Liabilities:
Contingent consideration	367	464
Recurring | Level 3 | Lazanda
Liabilities:
Contingent consideration		156
Recurring | Level 3 | CAMBIA
Liabilities:
Contingent consideration	510	993
Recurring | Level 3 | Corporate debt securities
Assets:
Total		0
Recurring | Level 3 | Money market funds
Assets:
Total	0	0
Recurring | Level 3 | Commercial paper
Assets:
Total	$ 0	$ 0