Consolidated Statement of Shareholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Loss
Increase (Decrease) in Stockholders' Equity
Adjustment as a result of the adoption of ASU 2016-06 Income Taxes - Intra-Entity Transfers Other than Inventory (Note 12)	$ (5,961)			$ (5,961)
Beginning Balance (in shares) at Dec. 31, 2017	173,507	173,507
Beginning Balance at Dec. 31, 2017	$ 1,095,673	$ 347	$ 461,338	668,587	$ (34,599)
Increase (Decrease) in Stockholders' Equity
Issuance of common stock under stock plans (in shares)		881
Issuance of common stock under stock plans	14,811	$ 2	14,809
Repurchase of common stock (in shares)		(2,356)
Repurchase of common stock	(121,308)	$ (5)		(121,303)
Stock-based compensation expense	22,196		22,196
Payment of dividends	(15,524)			(15,524)
Net income	93,413			93,413
Net unrealized gain (loss) on available-for-sale investments, net of tax of $(106)	(702)				(702)
Reclassification of net realized (gain) loss on the sale of available-for-sale investments	(269)				(269)
Foreign currency translation adjustment	$ (3,197)				(3,197)
Ending Balance (in shares) at Jul. 01, 2018	172,032	172,032
Ending Balance at Jul. 01, 2018	$ 1,079,132	$ 344	$ 498,343	$ 619,212	$ (38,767)