CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Operating activities:
Net income	$ 185,056	$ 75,323
Adjustments required to reconcile net income to net cash provided by operating activities:
Depreciation and amortization expense	9,936	8,100
Bad debt expense (recovery)	578	(8)
Stock-based compensation	43,757	29,170
Write-down of inventory and other	3,152	3,212
Accretion on marketable securities	(1,644)
Deferred tax provision	(25,992)	34,740
Change in fair value of contingent consideration	93	1,270
Changes in assets and liabilities:
Accounts receivable	(19,268)	(10,342)
Inventories	(26,522)	(11,974)
Prepaid expenses and other assets	678	(1,033)
Accounts payable	4,909	2,595
Accrued expenses and other liabilities	6,909	3,874
Deferred revenue	164	1,220
Net cash provided by operating activities	181,806	136,147
Investing activities:
Purchases of marketable securities	(241,745)	(209,834)
Proceeds from the sale and maturity of marketable securities	226,949	148,095
Purchase of other assets	(30,436)	(6,400)
Purchases of property and equipment	(35,469)	(44,168)
Net cash used for investing activities	(80,701)	(112,307)
Financing activities:
Proceeds from the exercise of stock options	11,043	7,626
Taxes paid related to net share settlement of vesting of stock awards	(71,213)	(19,860)
Proceeds from the issuance of stock under employee stock purchase plan	1,376	1,063
Principal payments on capital lease obligation		(517)
Net cash used for financing activities	(58,794)	(11,688)
Effect of exchange rate changes on cash	(1,105)	(690)
Net increase in cash and cash equivalents	41,206	11,462
Cash and cash equivalents at beginning of period	42,975	39,040
Cash and cash equivalents at end of period	84,181	50,502
Supplemental disclosure of cash flow information:
Cash paid for income taxes	4,500	845
Cash paid for interest on capital lease obligation		302
Supplemental disclosure of non-cash investing and financing activities:
Property and equipment in accounts payable and accrued expenses	$ 1,670	$ 3,836