Investments (Details) - USD ($) $ in Thousands	Dec. 30, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	$ 781,484	$ 316,086
Gross Unrealized Gains	2	3
Gross Unrealized Losses	(1,642)	(546)
Fair Value	779,844	315,543
Cash equivalents [Member]
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	160,548	34,587
Fair Value	160,548	34,587
Cash equivalents [Member] | Money market funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	99,472	23,110
Fair Value	99,472	23,110
Cash equivalents [Member] | Time deposits [Member]
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	60,226	11,477
Fair Value	60,226	11,477
Cash equivalents [Member] | Government and corporate bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	850
Fair Value	850
Short-term investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	435,458	185,693
Gross Unrealized Gains	2	3
Gross Unrealized Losses	(616)	(108)
Fair Value	434,844	185,588
Short-term investments [Member] | Time deposits [Member]
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	40,186	40,639
Fair Value	40,186	40,639
Short-term investments [Member] | Commercial paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	147,646	22,325
Gross Unrealized Gains	2
Gross Unrealized Losses	(139)	(24)
Fair Value	147,509	22,301
Short-term investments [Member] | Government and corporate bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	247,626	122,729
Gross Unrealized Gains		3
Gross Unrealized Losses	(477)	(84)
Fair Value	247,149	122,648
Long-term investments [Member] | Government and corporate bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	185,478	95,806
Gross Unrealized Losses	(1,026)	(438)
Fair Value	$ 184,452	$ 95,368