Significant Accounting Policies (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
	Jan. 01, 2018	Jun. 30, 2018	Jul. 01, 2017	Jun. 30, 2018	Jul. 01, 2017	Dec. 31, 2017
Assets:
Inventory, net	$ 455	$ 465		$ 465		$ 458
Prepaid expenses and other current assets	31	52		52		24
Long-term deferred income taxes	114	104		104		119
Other long-term assets	77	94		94		65
Liabilities:
Deferred revenue	184
Long-term deferred revenue	142
Stockholders’ Equity:
Retained earnings	1,267	1,446		1,446		1,248
Increase in liability related to changes in revenue recognition	1
Impact on revenue before new revenue recognition guidance		1,012	$ 896	1,989	$ 1,761
Calculated under Revenue Guidance in Effect before Topic 606
Assets:
Inventory, net						458
Prepaid expenses and other current assets						24
Long-term deferred income taxes						119
Other long-term assets						65
Liabilities:
Deferred revenue						186
Long-term deferred revenue						148
Stockholders’ Equity:
Retained earnings						$ 1,248
ASU 2014-09 | Calculated under Revenue Guidance in Effect before Topic 606
Stockholders’ Equity:
Impact on revenue before new revenue recognition guidance		$ (3)		$ (2)
ASU 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606
Assets:
Inventory, net	(3)
Prepaid expenses and other current assets	7
Long-term deferred income taxes	(5)
Other long-term assets	12
Liabilities:
Deferred revenue	(2)
Long-term deferred revenue	(6)
Stockholders’ Equity:
Retained earnings	19
Adjustment related to reallocation of revenue between performance obligations	$ (3)