CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Sep. 30, 2012	Sep. 30, 2011
Operating activities:
Net income (loss)	$ 8,588	$ (3,993)
Adjustments required to reconcile net income (loss) to net cash provided by (used for) operating activities:
Depreciation and amortization	1,449	2,125
Bad debt expense	6	65
Stock-based compensation	4,963	4,131
Write-down of inventory	598	376
Loss on disposal of fixed assets		29
Deferred tax provision	317	321
Changes in assets and liabilities:
Accounts receivable	1,606	(235)
Inventories	(4,208)	(2,562)
Prepaid expenses and other assets	(93)	114
Accounts payable	(1,155)	(1,854)
Accrued expenses and other long-term liabilities	(813)	(4,649)
Deferred revenue	(126)	(158)
Net cash provided by (used for) operating activities	11,132	(6,290)
Investing activities:
Purchases of short-term marketable securities	(18,750)	(8,001)
Proceeds from the sale and maturity of short-term marketable securities	5,500	7,000
Expenditures for property and equipment	(1,623)	(1,137)
Net cash used for investing activities	(14,873)	(2,138)
Financing activities:
Proceeds from the exercise of stock options	2,493	7,800
Payments in lieu of issuance of common stock for minimum payroll taxes	(238)
Proceeds from the issuance of stock under employee stock purchase plan	270	197
Net cash provided by financing activities	2,525	7,997
Effect of exchange rate changes on cash	(277)	(62)
Net decrease in cash and cash equivalents	(1,493)	(493)
Cash and cash equivalents at beginning of period	5,990	5,831
Cash and cash equivalents at end of period	4,497	5,338
Supplemental disclosures:
Fixed asset additions included in accounts payable	$ 93	$ 44