Leases (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 29, 2019	Jun. 30, 2018	Jun. 29, 2019	Jun. 30, 2018
Lessee Disclosure [Abstract]
Operating Lease, Weighted Average Remaining Lease Term	7 years 14 days		7 years 14 days
Lessee, Operating Lease, Description			we are the lessee under operating leases for real estate (office, data center, and warehouse space) and certain dedicated fiber optic lines within our infrastructure
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability			$ 23
Operating Lease, Cost	$ 10		19
Variable Lease, Cost			$ 1
Operating Lease, Weighted Average Discount Rate, Percent	3.70%		3.70%
Operating Leases, Rent Expense		$ 8		$ 17
Lessee, Operating Lease, Variable Lease Payment, Terms and Conditions			Generally, variable lease payments under these operating lease agreements relate to amounts based on changes to an index or rate (i.e. percentage change in the consumer price index)