Marketable Securities - Available for Sale Securities (Details) - USD ($) $ in Thousands	Dec. 30, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax	$ (517,724)	$ (423,029)
Short-term AFS securities
Amortized cost, short-term AFS securities	372,650	309,029
Gross unrealized gains, short-term AFS securities	1
Gross unrealized losses, short-term AFS securities	1,350	440
Fair value, short-term AFS securities	371,301	308,589
Long-term AFS securities
Amortized cost, long-term AFS securities	215,053	243,516
Gross unrealized gains, long-term AFS securities	52	0
Gross unrealized losses, long-term AFS securities	1,547	2,105
Fair value, long-term AFS securities	213,558	241,411
Corporate Debt Securities [Member]
Short-term AFS securities
Amortized cost, short-term AFS securities	140,631	150,334
Gross unrealized gains, short-term AFS securities	1
Gross unrealized losses, short-term AFS securities	464	227
Fair value, short-term AFS securities	140,168	150,107
Long-term AFS securities
Amortized cost, long-term AFS securities	130,612	92,687
Gross unrealized gains, long-term AFS securities	44	0
Gross unrealized losses, long-term AFS securities	1,032	683
Fair value, long-term AFS securities	129,624	92,004
US Treasury Securities [Member]
Short-term AFS securities
Amortized cost, short-term AFS securities	107,717	70,985
Gross unrealized gains, short-term AFS securities	0
Gross unrealized losses, short-term AFS securities	232	34
Fair value, short-term AFS securities	107,485	70,951
Long-term AFS securities
Amortized cost, long-term AFS securities	47,079	53,031
Gross unrealized gains, long-term AFS securities	5	0
Gross unrealized losses, long-term AFS securities	347	403
Fair value, long-term AFS securities	46,737	52,628
US Government Agency Securities [Member]
Short-term AFS securities
Amortized cost, short-term AFS securities	92,628	45,819
Gross unrealized gains, short-term AFS securities	0
Gross unrealized losses, short-term AFS securities	654	179
Fair value, short-term AFS securities	91,974	45,640
Long-term AFS securities
Amortized cost, long-term AFS securities	37,362	97,798
Gross unrealized gains, long-term AFS securities	3	0
Gross unrealized losses, long-term AFS securities	168	1,019
Fair value, long-term AFS securities	37,197	96,779
Certificates of Deposit [Member]
Short-term AFS securities
Amortized cost, short-term AFS securities	23,497	9,300
Gross unrealized gains, short-term AFS securities	0
Gross unrealized losses, short-term AFS securities	0	0
Fair value, short-term AFS securities	23,497	9,300
Commercial Paper [Member]
Short-term AFS securities
Amortized cost, short-term AFS securities	8,177	32,591
Gross unrealized gains, short-term AFS securities	0	0
Gross unrealized losses, short-term AFS securities	0	0
Fair value, short-term AFS securities	8,177	32,591
Debt Securities
Schedule of Available-for-sale Securities [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax	$ (2,800)	$ (2,500)