Finance Assets, net (Schedule of Allowance for Losses on Finance Assets) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance	$ 32	$ 42	$ 42
Decrease to allowance	(9)	(10)	0
Ending balance	$ 23	$ 32	$ 42