CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Income Statement [Abstract]
Net revenues	$ 210,300	$ 216,183	$ 414,226	$ 439,289
Cost of revenues	102,668	105,737	203,311	215,770
Gross profit	107,632	110,446	210,915	223,519
Operating expenses:
Research, development, and engineering	19,932	22,379	41,145	44,723
Selling, general, and administrative	57,696	56,875	113,929	112,662
(Gain) loss, net from litigation settlements	(104)	(349)	(280)	4,390
Restructuring and other related charges (credits)	(51)	(415)	2,522	(1,463)
Total operating expenses	77,473	78,490	157,316	160,312
Operating income	30,159	31,956	53,599	63,207
Interest expense	(7,260)	(7,257)	(14,563)	(14,545)
Other non-operating income and (expense), net	1,826	1,340	2,740	3,692
Income before income taxes	24,725	26,039	41,776	52,354
Income tax expense	4,772	5,565	2,995	11,493
Net income	$ 19,953	$ 20,474	$ 38,781	$ 40,861
Earnings per common share:
Basic (in dollars per share)	$ 0.59	$ 0.63	$ 1.16	$ 1.27
Diluted (in dollars per share)	$ 0.59	$ 0.63	$ 1.14	$ 1.24
Shares used in computing basic earnings per common share	32,570	32,281	32,538	32,269
Shares used in computing diluted earnings per common share	32,809	32,726	33,111	32,865
Cash dividends declared per common share (in dollars per share)	$ 0.15	$ 0.15	$ 0.3	$ 0.3