INCOME TAXES - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets:
Accrued expenses	$ 23,525	$ 22,234
NOL carryforwards	291,639	292,812
Tax credit carryforwards	89,397	78,715
Stock-based compensation	82,698	77,976
Other	30,106	42,331
Total deferred tax assets	517,365	514,068
Less valuation allowance	(115,853)	(132,598)
Net deferred tax assets	401,512	381,470
Deferred tax liabilities:
Investment in subsidiaries	(238,650)	(247,167)
Intangibles	(77,669)	(87,811)
Fair value investment	(22,927)
Other	(21,080)	(15,241)
Total deferred tax liabilities	(360,326)	(350,219)
Net deferred tax assets	$ 41,186	$ 31,251