DESCRIPTION OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning balance	$ 31,535
Ending balance	34,686	$ 31,535
Chargebacks
Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning balance	26,785	11,381	$ 6,865
Accruals/Adjustments	179,297	114,433	51,933
Credits Taken Against Reserve	(177,852)	(99,029)	(47,417)
Ending balance	28,230	26,785	11,381
Government Rebates
Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning balance	5,891	4,631	2,264
Accruals/Adjustments	12,237	9,671	6,719
Credits Taken Against Reserve	(10,198)	(8,411)	(4,352)
Ending balance	7,930	5,891	4,631
Returns
Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning balance	5,756	2,648	1,445
Accruals/Adjustments	12,184	10,271	2,808
Credits Taken Against Reserve	(9,666)	(7,163)	(1,605)
Ending balance	8,274	5,756	2,648
Administrative Fees and Other Rebates
Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning balance	3,550	1,653	1,487
Accruals/Adjustments	24,037	12,747	6,136
Credits Taken Against Reserve	(22,361)	(10,850)	(5,970)
Ending balance	5,226	3,550	1,653
Prompt Payment Discounts
Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning balance	1,554	674	471
Accruals/Adjustments	8,126	5,517	2,744
Credits Taken Against Reserve	(7,846)	(4,637)	(2,541)
Ending balance	$ 1,834	$ 1,554	$ 674