Additional Information (Schedule of Valuation and Qualifying Accounts) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Allowance, Discounts [Member]
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of year	$ 0	$ 0	$ 0
Charged to costs and expenses	620	626	628
Deductions	(620)	(626)	(628)
Balance at end of year	0	0	0
Allowance, Returned Goods [Member]
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of year	40	49	68
Charged to costs and expenses	97	130	133
Deductions	(105)	(139)	(152)
Balance at end of year	32	40	49
Allowance for losses on finance assets [Member]
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of year	23	32	42
Decrease to allowance	(4)	(9)	(10)
Balance at end of year	$ 19	$ 23	$ 32