CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Operating activities:
Net income	$ 61,877	$ 21,785
Adjustments required to reconcile net income to net cash provided by operating activities:
Depreciation expense	5,320	2,958
Bad debt expense	(54)	(13)
Stock-based compensation	17,938	18,047
Write-down of inventory and other assets	2,528	1,354
Excess tax benefit from stock-based awards		(3,631)
Deferred tax provision	3,073	9,777
Change in fair value of contingent consideration	682	186
Changes in assets and liabilities:
Accounts receivable	(2,824)	(3,807)
Inventories	(5,363)	(6,284)
Prepaid expenses and other assets	(869)	(2,029)
Accounts payable	299	1,906
Accrued expenses and other liabilities	(3,174)	3,157
Deferred revenue	18	330
Net cash provided by operating activities	79,451	43,736
Investing activities:
Purchases of marketable securities	(131,934)	(134,235)
Proceeds from the sale and maturity of marketable securities	95,416	116,685
Purchase of other investment	(6,400)
Purchases of property and equipment	(17,675)	(10,453)
Net cash used for investing activities	(60,593)	(28,003)
Financing activities:
Proceeds from the exercise of stock options	5,257	5,764
Excess tax benefit from stock-based awards		3,631
Taxes paid related to net share settlement of vesting of stock awards	(19,237)	(19,608)
Proceeds from the issuance of stock under employee stock purchase plan	1,063	769
Principal payments on capital lease obligation	(377)	(83)
Net cash used for financing activities	(13,294)	(9,527)
Effect of exchange rate changes on cash	(68)	272
Net increase in cash and cash equivalents	5,496	6,478
Cash and cash equivalents at beginning of period	39,040	48,231
Cash and cash equivalents at end of period	44,536	54,709
Supplemental disclosure of cash flow information:
Cash paid for income taxes	584	560
Cash paid for interest on capital lease obligation	259	89
Supplemental disclosure of non-cash investing and financing activities:
Property and equipment under capital lease obligation		16,784
Property and equipment in accounts payable and accrued expenses	$ 897	$ 3,810