NATURE OF OPERATIONS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Recent Accounting Pronouncements (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Equity investments without readily determinable fair value	$ 20,700	$ 20,700		$ 32,300
Impairment to carrying amount	10,100	10,100
Equity investments, fair value	$ 18,700	18,700		12,200
Cumulative effect of adoption of new accounting standard				2,100
Net cash flows from (used in) investing activities		(86,488)	$ 151,648
Net cash flows from (used in) financing activities		$ (257,875)	226,453
Accounting Standards Update 2016-01
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of adoption of new accounting standard				$ 2,100
Accounting Standards Update 2016-15
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net cash flows from (used in) investing activities			312,800
Net cash flows from (used in) financing activities			$ 1,500