PROPERTY, PLANT, AND EQUIPMENT - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Property, plant and equipment
Depreciation	$ 15,800	$ 6,300
Property, plant and equipment, at cost	558,861		$ 532,956
Laboratory equipment
Property, plant and equipment
Property, plant and equipment, at cost	120,362		104,008
Assets under construction	17,000
Expected cost to complete project	4,800
Leasehold and building improvements
Property, plant and equipment
Property, plant and equipment, at cost	109,737		80,352
Assets under construction	44,300
Expected cost to complete project	7,300
Computer equipment and computer software
Property, plant and equipment
Property, plant and equipment, at cost	68,830		65,323
Assets under construction
Property, plant and equipment
Property, plant and equipment, at cost	67,305		149,687
Computer software
Property, plant and equipment
Assets under construction	5,700
Expected cost to complete project	5,200
Furniture and fixtures
Property, plant and equipment
Property, plant and equipment, at cost	20,886		$ 14,539
Assets under construction	$ 300