CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Income Statement [Abstract]
Net revenues	$ 215,017	$ 215,805	$ 421,375	$ 432,467
Cost of revenues	104,047	97,978	203,047	199,930
Gross profit	110,970	117,827	218,328	232,537
Operating expenses:
Research, development, and engineering	22,609	23,769	45,803	46,289
Selling, general, and administrative	54,296	60,350	109,974	116,779
Gain from litigation settlements	(31)	(4,150)	(907)	(6,150)
Total operating expenses	76,874	79,969	154,870	156,918
Operating income	34,096	37,858	63,458	75,619
Interest expense	(7,320)	(142)	(10,061)	(150)
Other non-operating income and (expense), net	(2,138)	(543)	(2,423)	485
Income before income taxes	24,638	37,173	50,974	75,954
Income tax expense	6,742	9,752	11,850	19,861
Net income	$ 17,896	$ 27,421	$ 39,124	$ 56,093
Earnings per common share:
Basic (in dollars per share)	$ 0.53	$ 0.66	$ 1.09	$ 1.35
Diluted (in dollars per share)	$ 0.52	$ 0.65	$ 1.07	$ 1.32
Shares used in computing basic earnings per common share	33,590	41,765	35,796	41,692
Shares used in computing diluted earnings per common share	34,245	42,505	36,676	42,560
Cash dividends declared per common share (in dollars per share)	$ 0.15	$ 0.15	$ 0.30	$ 0.30