Condensed Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Jun. 30, 2014	Jun. 30, 2013
Operating activities:
Net loss	$ (1,709)	$ (1,723)
Adjustments required to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	621	652
Bad debt expense	31	15
Stock-based compensation	4,290	3,921
Write-down of inventory	206	207
Deferred tax provision	225	226
Changes in assets and liabilities:
Accounts receivable	1,548	1,971
Inventories	(234)	(1,689)
Prepaid expenses and other assets	(255)	292
Accounts payable	(1,049)	(1,302)
Accrued expenses and other long-term liabilities	(919)	(2,397)
Deferred revenue	435	(206)
Net cash provided by (used for) operating activities	3,190	(33)
Investing activities:
Purchases of marketable securities	(24,524)	(15,401)
Proceeds from the sale and maturity of marketable securities	35,730	17,750
Purchase of other investment		(750)
Purchases of property and equipment	(380)	(711)
Net cash provided by investing activities	10,826	888
Financing activities:
Proceeds from the exercise of stock options	820	1,931
Payments in lieu of issuance of common stock for minimum payroll taxes	(1,013)	(426)
Net cash (used for) provided by financing activities	(193)	1,505
Effect of exchange rate changes on cash	1	(84)
Net increase in cash and cash equivalents	13,824	2,276
Cash and cash equivalents at beginning of period	20,916	9,451
Cash and cash equivalents at end of period	34,740	11,727
Supplemental disclosures:
Cash paid for income taxes	172	798
Fixed asset expenditures incurred, not yet paid	$ 215	$ 86