CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands		12 Months Ended
		Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016
Cash flows from operating activities:
Net income		$ 27,177	$ 32,716	$ 31,630
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization		8,006	7,340	6,697
Investment premium amortization, net		1,092	666	1,180
Gain on sale of discontinued operations, net of tax		0	0	(559)
Net loss on disposals of property and equipment		102	115	103
Impairment loss of intangible assets		0	0	13
Foreign exchange (gain) loss		(996)	627	(149)
Share-based compensation expense		13,661	11,079	11,100
Excess tax benefits from share-based awards	[1]	0	(330)	(1,621)
Deferred income taxes		2,110	(1,319)	1,317
Equity in net (income) loss of unconsolidated affiliates		254	184	(22)
Gain on sale of equity method investment		(1,181)	(6,053)	0
Changes in assets and liabilities:
Receivables, net		(7,470)	(4,564)	(4,914)
Inventories		(8,181)	(8,184)	74
Prepaid expenses and other current assets		(228)	1,386	(1,912)
Other assets		(1,791)	(5,674)	(1,829)
Accounts payable		4,206	238	(443)
Accrued payroll and related expenses		1,674	1,257	(3,081)
Accrued taxes		(744)	760	(4,065)
Other liabilities		5,428	2,757	(4,848)
Deferred revenue		(535)	(999)	(667)
Warranty reserve		932	1,150	52
Net cash provided by operating activities		43,516	33,152	28,056
Cash flows from investing activities:
Purchases of available-for-sale investments		(109,448)	(4,401)	(2,731)
Purchases of held-to-maturity investments		(50,132)	(52,513)	(61,049)
Proceeds from maturities and redemptions of available-for-sale investments		39,460	4,300	0
Proceeds from maturities and redemptions of held-to-maturity investments		52,798	42,140	48,959
Purchases of property and equipment		(6,046)	(10,171)	(5,185)
Acquisitions, net of cash acquired		0	(785)	(1,131)
Cash paid for investment in unconsolidated affiliate		(1,250)	(2,999)	0
Proceeds from sale of equity method investment		1,181	8,526	0
Proceeds from sale of discontinued operations		0	0	900
Net cash used in investing activities		(73,437)	(15,903)	(20,237)
Cash flows from financing activities:
Tax withholdings related to net share settlements of restricted stock units		(2,590)	(2,234)	(5,250)
Excess tax benefits from share-based awards	[1]	0	330	1,621
Repurchases of common stock		0	0	(13,040)
Proceeds from the exercise of warrants		0	0	12
Dividends paid		(13,611)	(11,715)	(9,970)
Net cash used in financing activities		(16,201)	(13,619)	(26,627)
Effect of exchange rate changes on cash and cash equivalents		1,067	(621)	116
Net increase (decrease) in cash and cash equivalents		(45,055)	3,009	(18,692)
Cash and cash equivalents at beginning of year		91,332	88,323	107,015
Cash and cash equivalents at end of year		46,277	91,332	88,323
Supplemental disclosure of cash flow information:
Cash paid for income taxes, net of refunds		14,498	16,901	19,927
Supplemental disclosure of non-cash flow information:
Change in unrealized gain (loss) on investments, net of tax		(165)	(5)	1
Transfers of equipment between inventory and property and equipment, net		3,067	4,549	987
Net change in capitalized share-based compensation		(3)	47	14
Common stock withheld for employee taxes in connection with share-based compensation		2,590	2,234	5,250
Repayment of notes payable by credits from municipal agency		$ 101	$ 101	$ 101

[1] The Company adopted Accounting Standards Update ("ASU") No. 2016-09, "Improvements to Employee Share-based Payment Accounting" ("ASU 2016-09"), during the first quarter of fiscal 2018. This standard eliminates the requirement to reclassify cash flows related to excess tax benefits from operating activities to financing activities on the statements of cash flows. The Company adopted the guidance prospectively effective April 1, 2017. The adoption of ASU 2016-09 is discussed further in Note 1, "Description of Business and Summary of Significant Accounting Policies."