Significant Accounting Policies (Details) - USD ($) $ in Millions		3 Months Ended
	Jan. 01, 2018	Mar. 31, 2018	Dec. 31, 2017
Assets:
Inventory, net	$ 455	$ 448	$ 458
Prepaid expenses and other current assets	31	39	24
Long-term deferred income taxes	114
Other long-term assets	77	80	65
Liabilities:
Deferred revenue	184	201	186
Long-term deferred revenue	142	144	148
Stockholders’ Equity:
Retained earnings	1,267	1,376	1,248
Increase in liability related to changes in revenue recognition	1
Impact on revenue before new revenue recognition guidance		977
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
Accounting Standards Update 2014-09 | Calculated under Revenue Guidance in Effect before Topic 606
Stockholders’ Equity:
Impact on revenue before new revenue recognition guidance		$ 1
Accounting Standards Update 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)