Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
Operating activities:
Net income	$ 7,351	$ 15,014	$ 1,495
Adjustments required to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	2,508	2,723	4,336
Bad debt expense	47	33	117
Stock-based compensation	11,218	9,501	7,773
Write-down of inventory	2,012	1,172	1,833
Loss on disposal of fixed assets		10	53
Deferred tax provision	860	755	789
Gain on settlement of investment			(1,017)
Changes in assets and liabilities:
Accounts receivable	(1,312)	(2,586)	(5,284)
Inventories	(622)	(5,315)	(6,229)
Prepaid expenses and other assets	(1,039)	(326)	(239)
Accounts payable	(54)	1,183	287
Accrued expenses and other long-term liabilities	1,938	3,057	(1,330)
Deferred revenue	559	1,178	1,050
Net cash provided by operating activities	23,466	26,399	3,634
Investing activities:
Purchases of marketable securities	(87,026)	(49,429)	(24,502)
Proceeds from the sale and maturity of marketable securities	68,265	42,000	7,750
Purchase of other investment	(750)
Proceeds from settlement of investment			1,017
Purchases of property and equipment	(2,761)	(2,836)	(1,745)
Net cash used for investing activities	(22,272)	(10,265)	(17,480)
Financing activities:
Proceeds from the exercise of stock options	9,360	2,936	14,257
Repurchase of common stock		(15,045)
Payments in lieu of issuance of common stock for minimum payroll taxes	(425)	(257)
Proceeds from the issuance of stock under employee stock purchase plan	697	555	423
Net cash provided by (used for) financing activities	9,632	(11,811)	14,680
Effect of exchange rate changes on cash	639	(862)	(675)
Net increase in cash and cash equivalents	11,465	3,461	159
Cash and cash equivalents at beginning of year	9,451	5,990	5,831
Cash and cash equivalents at end of year	20,916	9,451	5,990
Supplemental disclosures:
Cash paid for income taxes	1,324	131	17
Fixed asset expenditures incurred, not yet paid	$ 60	$ 250	$ 535