Loans and finance receivables - Schedule of reconciliation of allowance for credit losses on loans and finance receivables (Detail) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
Allowance For Credit Loss [Abstract]
Balance at beginning of year	$ 167	$ 177
Adoption of ASC 326	486
Provision for credit losses	177	125
Charge-offs, net of recoveries	(118)	(135)
Balance at December 31	$ 712	$ 167

Effect of adopting new accounting pronouncement on allowance for credit losses.

No definition available.

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- References

No definition available.

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- Definition

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

+ References

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-Publisher FASB
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-Publisher FASB
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- Definition

Amount of writeoff of financing receivable, charged against allowance for credit loss.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
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- Definition

Amount of credit loss expense (reversal of expense) for financing receivable.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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