Debt - Automotive Asset-backed Notes - Additional Information (Detail) - Automotive Asset-backed Notes [Member] $ in Millions	3 Months Ended
Mar. 31, 2021 USD ($)
Debt Instrument [Line Items]
Debt principal issued	$ 1,980
Proceeds from issuance of secured debt	$ 1,970

Face (par) amount of debt instrument at time of issuance.

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Name:	us-gaap_DebtInstrumentFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant