NATURE OF OPERATIONS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Recent Accounting Pronouncements (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of classification change		$ 2,264
Net cash flows from operating activities	$ 591,766	402,927	$ 432,599
Net cash flows from (used in) financing activities	$ 124,249	(119,326)	702,335
Additional Paid-In Capital
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of classification change		431
Accumulated Deficit
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of classification change		1,833
Accounting Standards Update 2016-09 | New Accounting Pronouncement, Early Adoption, Effect
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net cash flows from operating activities		(2,200)	(2,100)
Net cash flows from (used in) financing activities		2,200	$ 2,100
Accounting Standards Update 2016-09 | New Accounting Pronouncement, Early Adoption, Effect | Additional Paid-In Capital
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of classification change		400
Accounting Standards Update 2016-09 | New Accounting Pronouncement, Early Adoption, Effect | Accumulated Deficit
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of classification change		$ (1,800)