Consolidated Statements of Stockholders' Equity (USD $) In Thousands, except Share data, unless otherwise specified	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Common Stock in Treasury
Beginning Balance at Mar. 31, 2011	$ 235,659	$ 1,470	$ 51,311	$ 320,024	$ (7)	$ (137,139)
Beginning Balance, shares at Mar. 31, 2011		14,703,084				4,969,679
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation expense	1,683		1,683
Issuance of common stock upon exercise of stock options	365			(562)		927
Issuance of common stock upon exercise of stock options, shares	42,577					26,478
Issuance of common stock under equity plan	(60)			(374)		314
Issuance of common stock under equity plan, shares						7,495
Purchase of treasury shares	(1,648)					(1,648)
Purchase of treasury shares, shares	(88,210)					(88,210)
Tax effect of stock awards	(26)		(26)
Reduction of deferred tax assets due to expired stock options	(2,585)		(2,585)
Foreign currency translation adjustment	1				1
Cash dividends ($.60 per common share)	(5,837)			(5,837)
Postretirement medical plan, net of tax	(19)				(19)
Net income	15,670			15,670
Ending Balance at Mar. 31, 2012	243,203	1,470	50,383	328,921	(25)	(137,546)
Ending Balance, shares at Mar. 31, 2012		14,703,084				5,023,916
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adjustment (see Note 7)	0		(1,727)	1,727
Share-based compensation expense	1,783		1,783
Issuance of common stock upon exercise of stock options	192			(193)		385
Issuance of common stock upon exercise of stock options, shares	11,000					11,000
Issuance of common stock under equity plan	(262)			(1,487)		1,225
Issuance of common stock under equity plan, shares						28,784
Purchase of treasury shares	(4,864)					(4,864)
Purchase of treasury shares, shares	(251,180)					(251,180)
Tax effect of stock awards	(6)		(6)
Reduction of deferred tax assets due to expired stock options	(549)		(549)
Foreign currency translation adjustment	0
Cash dividends ($.60 per common share)	(5,731)			(5,731)
Postretirement medical plan, net of tax	(15)				(15)
Net income	15,227			15,227
Ending Balance at Mar. 31, 2013	248,978	1,470	49,884	338,464	(40)	(140,800)
Ending Balance, shares at Mar. 31, 2013		14,703,084				5,235,312
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation expense	1,843		1,843
Issuance of common stock upon exercise of stock options	49			(2,044)		2,093
Issuance of common stock upon exercise of stock options, shares	182,378					59,793
Issuance of common stock under equity plan	(563)			(2,083)		1,520
Issuance of common stock under equity plan, shares						39,928
Purchase of treasury shares	(6,634)					(6,634)
Purchase of treasury shares, shares	(272,655)					(272,655)
Tax effect of stock awards	425		425
Reduction of deferred tax assets due to expired stock options	(35)		(35)
Foreign currency translation adjustment	0
Cash dividends ($.60 per common share)	(5,637)			(5,637)
Postretirement medical plan, net of tax	21				21
Net income	18,769			18,769
Ending Balance at Mar. 31, 2014	$ 257,216	$ 1,470	$ 52,117	$ 347,469	$ (19)	$ (143,821)
Ending Balance, shares at Mar. 31, 2014		14,703,084				5,408,246