CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Oct. 01, 2017	Sep. 30, 2018	Oct. 01, 2017
Revenues:
Total revenues	$ 566,848	$ 503,378	$ 1,581,244	$ 1,657,191
Cost of revenues:
Total cost of revenues (exclusive of acquired intangible assets amortization shown separately below)	233,155	208,509	670,385	706,667
Gross profit	333,693	294,869	910,859	950,524
Operating expenses:
Selling and administrative	100,199	86,130	290,115	261,034
Engineering and development	77,049	76,986	226,799	235,235
Acquired intangible assets amortization	11,142	7,028	28,633	23,145
Restructuring and other	1,710	(4,407)	3,785	392
Total operating expenses	190,100	165,737	549,332	519,806
Income from operations	143,593	129,132	361,527	430,718
Non-operating (income) expense:
Interest income	(6,213)	(4,517)	(17,620)	(11,329)
Interest expense	5,557	5,372	18,087	16,283
Other (income) expense, net	3,405	840	4,385	(565)
Income before income taxes	140,844	127,437	356,675	426,329
Income tax provision	20,863	24,017	48,684	62,713
Net income	$ 119,981	$ 103,420	$ 307,991	$ 363,616
Net income per common share:
Basic	$ 0.65	$ 0.52	$ 1.62	$ 1.83
Diluted	$ 0.63	$ 0.52	$ 1.57	$ 1.81
Weighted average common shares-basic	185,744	197,485	190,576	198,755
Weighted average common shares-diluted	190,505	200,775	196,300	201,413
Cash dividend declared per common share	$ 0.09	$ 0.07	$ 0.27	$ 0.21
Product [Member]
Revenues:
Total revenues	$ 470,994	$ 412,854	$ 1,308,969	$ 1,396,413
Cost of revenues:
Total cost of revenues (exclusive of acquired intangible assets amortization shown separately below)	195,339	169,661	557,074	592,294
Service [Member]
Revenues:
Total revenues	95,854	90,524	272,275	260,778
Cost of revenues:
Total cost of revenues (exclusive of acquired intangible assets amortization shown separately below)	$ 37,816	$ 38,848	$ 113,311	$ 114,373