Financing Receivables - Past Due (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Past Due Financing Receivable
Amortized Cost	$ 14,980	$ 18,242
Total Client Financing Receivables Portfolio Segment
Past Due Financing Receivable
Amortized Cost	13,861	15,822
Amortized Cost Not Accruing	212	223
Impaired financing receivables, related allowance	167	178
Total Client Financing Receivables Portfolio Segment | Total Past Due > 90 days
Past Due Financing Receivable
Amortized Cost > 90 Days	405	456
Amortized Cost > 90 Days and Accruing	205	241
Billed Invoices > 90 Days and Accruing	18	20
Total Client Financing Receivables Portfolio Segment | Americas
Past Due Financing Receivable
Amortized Cost	6,867	7,758
Amortized Cost Not Accruing	94	96
Total Client Financing Receivables Portfolio Segment | Americas | Total Past Due > 90 days
Past Due Financing Receivable
Amortized Cost > 90 Days	271	295
Amortized Cost > 90 Days and Accruing	182	200
Billed Invoices > 90 Days and Accruing	11	12
Total Client Financing Receivables Portfolio Segment | EMEA
Past Due Financing Receivable
Amortized Cost	4,244	5,023
Amortized Cost Not Accruing	93	95
Total Client Financing Receivables Portfolio Segment | EMEA | Total Past Due > 90 days
Past Due Financing Receivable
Amortized Cost > 90 Days	102	119
Amortized Cost > 90 Days and Accruing	14	28
Billed Invoices > 90 Days and Accruing	3	5
Total Client Financing Receivables Portfolio Segment | Asia Pacific
Past Due Financing Receivable
Amortized Cost	2,750	3,042
Amortized Cost Not Accruing	24	32
Total Client Financing Receivables Portfolio Segment | Asia Pacific | Total Past Due > 90 days
Past Due Financing Receivable
Amortized Cost > 90 Days	32	42
Amortized Cost > 90 Days and Accruing	9	12
Billed Invoices > 90 Days and Accruing	$ 4	$ 4