Long-term Financing and Sales of Receivables - Sales Receivables (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jul. 01, 2017	Jun. 30, 2018	Jul. 01, 2017	Dec. 31, 2017
Receivables [Abstract]
Accounts receivable sales proceeds	$ 22	$ 61	$ 76	$ 80
Long-term receivables sales proceeds	15	22	28	68
Total proceeds from receivable sales	37	$ 83	104	$ 148
Servicing obligations for long-term receivables	$ 844		$ 844		$ 873