Financing Receivables - By Portfolio Segment (Details) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2021 USD ($) item	Dec. 31, 2020 USD ($) item
Financing receivables
Number of classes of financing receivable | item	3	3
Amortized Cost	$ 14,096	$ 18,242
Allowance for credit losses:
Allowance for credit losses, beginning balance	263
Allowance for credit losses, ending balance	228	263
Client Financing Receivables
Financing receivables
Amortized Cost	13,077	15,822
Allowance for credit losses:
Allowance for credit losses, beginning balance	255	252
Write-offs	(12)	(34)
Recoveries	1	3
Additions/(releases)	(22)	34
Other	(1)	1
Allowance for credit losses, ending balance	221	255
Client Financing Receivables | Americas
Financing receivables
Amortized Cost	6,538	7,758
Allowance for credit losses:
Allowance for credit losses, beginning balance	141	142
Write-offs	(4)	(28)
Recoveries	0	0
Additions/(releases)	(16)	33
Other	1	(6)
Allowance for credit losses, ending balance	122	141
Client Financing Receivables | EMEA
Financing receivables
Amortized Cost	4,039	5,023
Allowance for credit losses:
Allowance for credit losses, beginning balance	77	69
Write-offs	(1)	(3)
Recoveries	0	0
Additions/(releases)	(2)	5
Other	(2)	6
Allowance for credit losses, ending balance	73	77
Client Financing Receivables | Asia Pacific
Financing receivables
Amortized Cost	2,500	3,042
Allowance for credit losses:
Allowance for credit losses, beginning balance	37	41
Write-offs	(7)	(3)
Recoveries	1	2
Additions/(releases)	(4)	(4)
Other	0	1
Allowance for credit losses, ending balance	$ 26	$ 37