COMMITMENTS AND CONTINGENCIES - Narrative (Details) $ in Thousands			2 Months Ended	12 Months Ended
	Nov. 06, 2019 defendant	Sep. 25, 2019 USD ($)	Jan. 13, 2020 lawsuit	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Jan. 01, 2019 USD ($)
Commitments
Operating lease liability				$ 23,868
Operating lease right-of-use asset				$ 23,286
Weighted average operating lease remaining lease term				7 years 11 months 12 days
Weighted average operating lease discount rate				5.10%
Lease cost for operating leases				$ 5,100
Lease cost for operating leases					$ 5,100	$ 3,000
Operating cash outflows from operating leases				5,200
Remaining minimum purchase commitments				$ 105,900
Minimum
Commitments
Remaining operating lease term				1 year
Maximum
Commitments
Remaining operating lease term				8 years 6 months
Accounting Standards Update 2016-02
Commitments
Operating lease liability				$ 23,900			$ 8,500
Operating lease right-of-use asset							$ 7,600
Subsequent Event | Pending Litigation
Commitments
Number of class action lawsuits filed | lawsuit			4
Civil Case In Saginaw Chippewa Indian Tribe V. Purdue Pharma Et Al | Pending Litigation
Commitments
Number of other pharmaceutical companies named as defendants | defendant	40
Lunar Representative, LLC V. AMAG Pharmaceuticals, Inc. | Pending Litigation
Commitments
Damages sought by plaintiff		$ 50,000