Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jul. 01, 2017
Statement of Cash Flows [Abstract]
Cash and cash equivalents at beginning of period	$ 688,087	$ 465,232
Cash flows from operating activities:
Net income	148,034	137,386
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	59,282	58,304
Amortization of debt discount and fees	586	633
Stock-based compensation	78,857	57,918
Gain on investments, net	(2,136)	(2,083)
Deferred income taxes	1,664	4,813
Provisions for losses on receivables	1,015	0
Other non-cash items	462	2,157
Changes in operating assets and liabilities, net of effect of acquired businesses:
Receivables	(2,606)	6,342
Inventories	1,932	2,535
Prepaid expenses and other	13,294	(1,557)
Other assets	5,622	(8,790)
Accounts payable and accrued liabilities	(11,832)	(21,995)
Deferred revenue	71,667	18,733
Other long-term liabilities	(2,928)	174
Net cash provided by operating activities	362,913	254,570
Cash flows from investing activities:
Proceeds from the sale of available-for-sale securities	0	189
Purchases of property, plant and equipment	(31,105)	(27,488)
Net cash used for investing activities	(31,105)	(27,299)
Cash flows from financing activities:
Proceeds from revolving credit facility	0	50,000
Payment on revolving credit facility	(85,000)	(100,000)
Payment of debt issuance costs	0	(793)
Proceeds from issuance of common stock	25,656	29,967
Stock received for payment of employee taxes on vesting of restricted stock	(30,125)	(25,819)
Payments for repurchases of common stock	(100,025)	0
Change in book overdraft	(3,867)	0
Net cash used for financing activities	(193,361)	(46,645)
Effect of exchange rate changes on cash and cash equivalents	(6,994)	10,140
Increase in cash and cash equivalents	131,453	190,766
Cash and cash equivalents at end of period	819,540	655,998
Supplemental cash flow information:
Cash paid for interest	13,165	12,112
Cash paid for taxes, net	$ 17,807	$ 27,236