CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Cash flows from operating activities:
Net income	$ 3,229	$ 2,864
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	1,735	1,441
Investment premium amortization, net	185	240
Net loss on disposals of property and equipment	0	20
Net (gain) loss on foreign exchange translation	(115)	392
Share-based compensation expense	2,249	1,802
Excess tax benefits from share-based awards	(1,397)	(717)
Provision for deferred income taxes	(253)	(177)
Equity in net income of unconsolidated affiliate	(30)	(17)
Changes in assets and liabilities:
Receivables, net	7,708	1,569
Inventories	(1,096)	(1,740)
Prepaid expenses and other current assets	2,356	2,439
Other assets	7	(27)
Accounts payable	(1,958)	1,178
Accrued payroll and related expenses	(128)	496
Accrued taxes	(105)	(111)
Other accrued liabilities	(178)	(185)
Deferred rent	11	28
Deferred revenue	(6)	407
Warranty reserve	(57)	(352)
Net cash provided by operating activities	12,157	9,550
Cash flows from investing activities:
Purchases of held-to-maturity investments	(8,036)	(4,407)
Proceeds from maturities and redemptions of held-to-maturity investments	12,127	7,251
Purchases of property and equipment	(1,228)	(1,733)
Net cash provided by investing activities	2,863	1,111
Cash flows from financing activities:
Proceeds from the exercise of stock options	17	77
Tax withholdings related to net share settlements of restricted stock units	(3,712)	(823)
Excess tax benefits from share-based awards	1,397	717
Net cash used in financing activities	(2,298)	(29)
Effect of exchange rate changes on cash and cash equivalents	154	(324)
Net increase in cash and cash equivalents	12,876	10,308
Cash and cash equivalents at beginning of period	54,910	45,843
Cash and cash equivalents at end of period	67,786	56,151
Supplemental disclosure of cash flow information:
Cash paid for income taxes, net of refunds	189	148
Supplemental disclosure of non-cash flow information:
Change in unrealized gain (loss) on investments, net of tax	(13)	(4)
Transfers of equipment between inventory and property and equipment, net	402	439
Net change in capitalized share-based compensation	50	42
Common stock withheld for employee taxes in connection with share-based compensation	3,712	823
Repayment of notes payable by credits from municipal agency	$ 25	$ 25