QUARTERLY RESULTS OF OPERATIONS - UNAUDITED (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Revenue	$ 235,002	$ 246,008	$ 223,797	$ 205,111	$ 235,224	$ 268,944	$ 256,863	$ 225,756	$ 909,918	$ 986,787	$ 1,162,112
Gross profit	176,466	176,424	159,817	143,084	168,633	204,435	182,620	159,194	655,791	714,882	815,973
Net income (loss)	$ 19,211	$ (3,603)	$ (26,428)	$ (62,504)	$ 16,817	$ 89,685	$ (2,468)	$ (24,222)	$ (73,324)	$ 79,812	$ 33,291
Diluted net income (loss) per share (in dollars per share)	$ 0.24	$ (0.05)	$ (0.34)	$ (0.78)	$ 0.20	$ 1.02	$ (0.03)	$ (0.27)	$ (0.93)	$ 0.90	$ 0.36