CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ 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
Income Statement [Abstract]
Net revenue	$ 539,007	$ 1,248,738	$ 492,667	$ 387,982	$ 450,274	$ 480,840	$ 443,562	$ 418,216	$ 2,668,394	$ 1,792,892		$ 1,779,748
Cost of goods sold									1,523,644	898,311		1,022,959
Gross profit	280,092	350,254	257,787	256,617	261,063	212,857	197,014	223,647	1,144,750	894,581		756,789
Selling and marketing									391,400	256,092		285,453
General and administrative									281,234	247,828		211,409
Research and development									230,170	196,373		137,915
Depreciation and amortization									40,232	43,969		30,707
Business reorganization									(4,958)	14,742		0
Total operating expenses									938,078	759,004		665,484
Income from operations	58,061	51,779	25,986	70,846	87,825	8,852	(11,319)	50,219	206,672	135,577		91,305
Interest and other, net									26,113	1,048		(15,690)
Gain on long-term investments, net									0	0	[1]	1,350	[1]
Income before income taxes									232,785	136,625		76,965
(Benefit from) provision for income taxes									(101,052)	(36,908)		9,662
Net income	$ 56,829	$ 179,948	$ 25,367	$ 71,693	$ 90,853	$ 25,140	$ (2,736)	$ 60,276	$ 333,837	$ 173,533	[1]	$ 67,303	[1]
Earnings per share:
Basic earnings per share (in dollars per share)	$ 0.50	$ 1.59	$ 0.22	$ 0.63	$ 0.80	$ 0.22	$ (0.03)	$ 0.57	$ 2.95	$ 1.57		$ 0.73
Diluted earnings per share (in dollars per share)	$ 0.50	$ 1.57	$ 0.22	$ 0.62	$ 0.77	$ 0.21	$ (0.03)	$ 0.56	$ 2.90	$ 1.54		$ 0.72

[1] Prior period amounts have been adjusted retrospectively to reflect the adoption of ASU 2016-18, Statement of Cash Flows (Topic 230): RestrictedCash. Refer to Note 1 for further discussion.