Financing Receivables - By Portfolio Segment (Details) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2021 USD ($) item	Dec. 31, 2020 USD ($) item
Financing receivables
Number of classes of financing receivable | item	3	3
Amortized Cost	$ 14,980	$ 18,242
Allowance for credit losses:
Allowance for credit losses, beginning balance	263
Allowance for credit losses, ending balance	236	263
Total Client Financing Receivables Portfolio Segment
Financing receivables
Amortized Cost	13,861	15,822
Allowance for credit losses:
Allowance for credit losses, beginning balance	255	252
Write-offs	(9)	(34)
Recoveries	1	3
Additions/(releases)	(12)	34
Other	(6)	1
Allowance for credit losses, ending balance	229	255
Total Client Financing Receivables Portfolio Segment | Americas
Financing receivables
Amortized Cost	6,867	7,758
Allowance for credit losses:
Allowance for credit losses, beginning balance	141	142
Write-offs	(2)	(28)
Recoveries	0	0
Additions/(releases)	(11)	33
Other	(3)	(6)
Allowance for credit losses, ending balance	125	141
Total Client Financing Receivables Portfolio Segment | EMEA
Financing receivables
Amortized Cost	4,244	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	(3)	6
Allowance for credit losses, ending balance	76	77
Total Client Financing Receivables Portfolio Segment | Asia Pacific
Financing receivables
Amortized Cost	2,750	3,042
Allowance for credit losses:
Allowance for credit losses, beginning balance	37	41
Write-offs	(6)	(3)
Recoveries	0	2
Additions/(releases)	(3)	(4)
Other	0	1
Allowance for credit losses, ending balance	$ 27	$ 37