Loans and finance receivables - Schedule of reconciliation of allowance for credit losses on loans and finance receivables (Detail) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Allowance For Credit Loss [Abstract]
Balance at beginning of year	$ 712	$ 167
Adoption of ASC 326		486
Provision for credit losses	65	177
Charge-offs, net of recoveries	(33)	(99)
Balance at September 30	$ 744	$ 731