CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) (USD $) In Thousands	6 Months Ended
	Sep. 30, 2011	Sep. 30, 2010
Cash flows from operating activities:
Net income	$ 5,535	$ 7,329
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	2,435	2,196
Investment premium amortization, net	503	191
Net loss on disposals of property and equipment	8	5
Net loss (gain) on foreign exchange translation	141	(233)
Share-based compensation expense	2,682	2,249
Excess tax benefits from share-based awards	(486)	(489)
Provision for deferred income taxes	374	476
Equity in net loss of unconsolidated affiliate	72	0
Changes in assets and liabilities:
Receivables, net	288	(1,016)
Inventories	41	716
Prepaid expenses and other current assets	(1,144)	(719)
Other assets	20	(27)
Accounts payable	839	(3,925)
Accrued payroll and related expenses	744	139
Accrued taxes	(316)	302
Other accrued liabilities	96	(39)
Deferred rent	114	165
Deferred revenue	518	133
Warranty reserve	214	(492)
Net cash provided by operating activities	12,678	6,961
Cash flows from investing activities:
Purchases of held-to-maturity investments	(18,174)	(35,438)
Proceeds from maturities and redemptions of held-to-maturity investments	33,141	43,933
Purchases of property and equipment	(4,777)	(1,725)
Net cash provided by investing activities	10,190	6,770
Cash flows from financing activities:
Proceeds from notes payable from municipal agency	147	0
Proceeds from the exercise of stock options	430	449
Tax withholdings related to net share settlements of restricted stock units	(2,019)	(1,969)
Repurchases of common stock	(27,328)	0
Excess tax benefits from share-based awards	486	489
Net cash used in financing activities	(28,284)	(1,031)
Effect of exchange rate changes on cash and cash equivalents	(61)	93
Net (decrease) increase in cash and cash equivalents	(5,477)	12,793
Cash and cash equivalents at beginning of period	43,471	27,857
Cash and cash equivalents at end of period	37,994	40,650
Supplemental disclosure of cash flow information:
Cash paid for income taxes, net of refunds	2,796	3,759
Supplemental disclosure of non-cash flow information:
Transfers of equipment between inventory and property and equipment, net	645	417
Net change in capitalized share-based compensation	(19)	16
Common stock withheld for employee taxes in connection with share-based compensation	2,019	1,969
Repayment of notes payable by credits from municipal agency	$ 44	$ 0