Loans and finance receivables (Detail) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019	Sep. 30, 2019	Dec. 31, 2018
Receivables [Abstract]
Loans and finance receivables before allowances and discounts	$ 19,832	$ 18,199
Allowances for credit losses	(731)	(167)	$ (183)	$ (177)
Unamortized acquisition discounts and points	(517)	(505)
Loans and finance receivables	$ 18,584	$ 17,527

Amount of allowance for credit loss on financing receivable. Excludes allowance for financing receivable covered under loss sharing agreement.

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