Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Operating activities:
Net (loss) income	$ (664)	$ 8,588
Adjustments required to reconcile net (loss) income to net cash provided by operating activities:
Depreciation and amortization	1,322	1,449
Bad debt expense	15	6
Stock-based compensation	6,719	4,963
Write-down of inventory	537	598
Deferred tax provision	453	317
Changes in assets and liabilities:
Accounts receivable	1,912	1,606
Inventories	(876)	(4,208)
Prepaid expenses and other assets	(762)	(93)
Accounts payable	(1,494)	(1,155)
Accrued expenses and other long-term liabilities	(1,978)	(813)
Deferred revenue	(62)	(126)
Net cash provided by operating activities	5,122	11,132
Investing activities:
Purchases of marketable securities	(33,849)	(18,750)
Proceeds from the sale and maturity of marketable securities	25,750	5,500
Purchase of other investment	(750)
Purchases of property and equipment	(1,236)	(1,623)
Net cash used for investing activities	(10,085)	(14,873)
Financing activities:
Proceeds from the exercise of stock options	5,318	2,493
Payments in lieu of issuance of common stock for minimum payroll taxes	(426)	(238)
Proceeds from the issuance of stock under employee stock purchase plan	312	270
Net cash provided by financing activities	5,204	2,525
Effect of exchange rate changes on cash	428	(277)
Net increase (decrease) in cash and cash equivalents	669	(1,493)
Cash and cash equivalents at beginning of period	9,451	5,990
Cash and cash equivalents at end of period	10,120	4,497
Supplemental disclosures:
Fixed asset expenditures incurred, not yet paid	$ 92	$ 93