CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2014
Cash flows from operating activities:
Net income	$ 31,630	$ 27,331	$ 14,185
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	6,697	8,486	7,427
Investment premium amortization, net	1,180	635	530
Gain on sale of discontinued operations, net of tax	(559)	(7,682)	0
Net loss on disposals of property and equipment	103	8	20
Impairment loss of intangible assets	13	0	0
Foreign exchange (gain) loss	(149)	1,794	(477)
Share-based compensation expense	11,100	9,787	7,643
Excess tax benefits from share-based awards	(1,621)	(961)	(2,164)
Deferred income taxes	1,317	(3,954)	(785)
Equity in net income of unconsolidated affiliate	(22)	(37)	(33)
Changes in assets and liabilities:
Receivables, net	(4,914)	(1,306)	11,171
Inventories	74	(10,135)	(2,491)
Prepaid expenses and other current assets	(1,912)	787	2,962
Other assets	(1,829)	(55)	21
Accounts payable	(443)	116	(2,018)
Accrued payroll and related expenses	(3,081)	6,776	(1,626)
Accrued taxes	(4,065)	(1,294)	690
Other liabilities	(4,848)	5,514	(98)
Deferred revenue	(667)	(702)	131
Warranty reserve	52	1,288	484
Net cash provided by operating activities	28,056	36,396	35,572
Cash flows from investing activities:
Purchases of available-for-sale investments	(2,731)	0	(4,384)
Purchases of held-to-maturity investments	(61,049)	(36,804)	(27,798)
Proceeds from maturities and redemptions of available-for-sale investments	0	6,498	1,023
Proceeds from maturities and redemptions of held-to-maturity investments	48,959	26,969	23,311
Purchases of property and equipment	(5,185)	(6,077)	(5,554)
Proceeds from disposals of property and equipment	0	25	44
Acquisitions, net of cash acquired	(1,131)	(618)	0
Proceeds from sale of discontinued operations	900	20,100	0
Net cash provided by (used in) investing activities	(20,237)	10,093	(13,358)
Cash flows from financing activities:
Proceeds from the exercise of stock options	0	31	1,455
Tax withholdings related to net share settlements of restricted stock units	(5,250)	(3,026)	(4,683)
Excess tax benefits from share-based awards	1,621	961	2,164
Repurchases of common stock	(13,040)	0	(2,981)
Proceeds from the exercise of warrants	12	78	0
Dividends paid	(9,970)	(9,006)	0
Net cash used in financing activities	(26,627)	(10,962)	(4,045)
Effect of exchange rate changes on cash and cash equivalents	116	(2,101)	510
Net increase (decrease) in cash and cash equivalents	(18,692)	33,426	18,679
Cash and cash equivalents at beginning of year	107,015	73,589	54,910
Cash and cash equivalents at end of year	88,323	107,015	73,589
Supplemental disclosure of cash flow information:
Cash paid for income taxes, net of refunds	19,927	15,888	4,943
Supplemental disclosure of non-cash flow information:
Change in unrealized gain (loss) on investments, net of tax	1	(3)	(47)
Transfers of equipment between inventory and property and equipment, net	987	2,295	2,285
Net change in capitalized share-based compensation	14	(29)	(14)
Common stock withheld for employee taxes in connection with share-based compensation	5,250	3,026	4,683
Repayment of notes payable by credits from municipal agency	101	101	101
Settlement of preexisting business relationship in connection with acquisition	0	931	0
Installment payment obligation accrued related to acquisition	$ 0	$ 2,336	$ 0