Consolidated Statements of Comprehensive Income (Unaudited) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 27, 2015	Mar. 28, 2014
Income Statement [Abstract]
Net sales	$ 435,485	$ 461,092
Cost of sales	156,263	151,868
Gross margin	279,222	309,224
Research and development expense	103,231	97,657
Selling, general, and administrative expense	70,506	74,507
Amortization of acquisition-related intangible assets	2,464	2,465
Compensation expense — deferred compensation plan	27	1,454
Gain on deferred compensation plan securities	(27)	(1,454)
Interest income and other	(6,596)	(5,985)
Gain reclassified from other comprehensive income	(2,506)	(48)
Interest expense	10,408	10,488
Income before income taxes	101,715	130,140
Income tax expense	6,863	13,626
Net income	94,852	116,514
Unrealized holding gain on investments:
Unrealized holding gain on investments arising during period, net of tax of $41 and $24	16,785	12,560
Less: Reclassification adjustments for gain on investments included in net income, net of tax of $6 and $4	(2,500)	(44)
Other comprehensive income	14,285	12,516
Comprehensive income	$ 109,137	$ 129,030
Net income per share (in dollars per share):
Basic (in dollars per share)	$ 0.31	$ 0.37
Diluted (in dollars per share)	$ 0.31	$ 0.37
Shares used in computing per share amounts (in shares):
Basic (in shares)	301,308	316,552
Diluted (in shares)	303,285	318,901
Dividends per common share	$ 0.18	$ 0.15