INCOME TAXES - Tax Effects of Temporary Differences and Related Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets:
Capitalized costs	$ 23,708	$ 30,131	$ 35,608
Accrued expenses	33,044	31,494	23,553
Net operating loss carryforwards	575,245	485,562	244,197
Tax credit carryforwards	183,977	133,275	60,567
Property, equipment and intangible assets	0	0	7,390
Share-based compensation	38,427	38,265	35,728
Deferred Interest	4,072	8,290	0
Other	3,424	105	2,519
Operating Lease, net	5,761	0	0
Total deferred tax assets	867,658	727,122	409,562
Valuation allowance	(859,564)	(719,040)	(409,043)
Total deferred tax assets, net of valuation allowance	8,094	8,082	519
Deferred tax liabilities:
Property, equipment and intangible assets	(6,862)	(7,361)	0
Indefinite-lived intangibles	(253)	(275)	(644)
Total deferred tax liabilities	(7,115)	(7,636)	(644)
Net deferred tax asset	$ 979	$ 446
Net deferred tax liabilities			$ (125)