Components Of Vehicle Depreciation And Lease Charges (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Vehicle Depreciation and Lease Charges, Net [Line Items]
Depreciation expense	$ 1,330	$ 1,890	$ 1,974
Lease charges	195	255	253
(Gain) loss on sale of vehicles, net	(157)	(82)	(48)
Vehicle depreciation and lease charges, net	1,368	2,063	2,179
Accounts Payable, Other, Current	232	418	472
Receivables due from former subsidiaries	$ 162	$ 576	$ 622