Goodwill, Customer Relationships and Other Intangible Assets - Additional Information (Details)				3 Months Ended		12 Months Ended
	Oct. 31, 2020 USD ($) reporting_unit	Oct. 31, 2019 reporting_unit	Oct. 31, 2018 USD ($) reporting_unit	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Jan. 01, 2019
Finite-Lived Intangible Assets [Line Items]
Number of reporting units | reporting_unit	8	8	5
Weighted average cost of capital, percentage	7.60%	6.30%
Cost of debt, after tax, percentage	2.50%	4.40%
Cost of equity, percentage	10.70%	7.60%
Control premium, percent	33.00%	44.70%	0.10%	4.10%					4.50%
Goodwill impairment	$ 2,600,000,000			$ 6,500,000,000		$ 2,642,000,000	$ 6,506,000,000	$ 2,726,000,000
Number of reporting units with no goodwill impairment | reporting_unit			4
Impairment of indefinite-lived intangible assets						$ 0	0
Acquired finite-lived intangible assets, weighted average useful life						8 years
Amortization of intangible assets						$ 1,700,000,000	$ 1,700,000,000	$ 1,800,000,000
Intangible assets, gross (including goodwill)						$ 41,500,000,000
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Acquired finite-lived intangible assets, weighted average useful life						9 years
Capitalized software
Finite-Lived Intangible Assets [Line Items]
Acquired finite-lived intangible assets, weighted average useful life						3 years
Trade names
Finite-Lived Intangible Assets [Line Items]
Acquired finite-lived intangible assets, weighted average useful life						2 years
Measurement Input, Revenue Multiple
Finite-Lived Intangible Assets [Line Items]
Goodwill impairment, measurement input	2.3	2.3
Measurement Input, Revenue Multiple | Minimum
Finite-Lived Intangible Assets [Line Items]
Goodwill impairment, measurement input	2.0	2.3		2.1
Measurement Input, Revenue Multiple | Maximum
Finite-Lived Intangible Assets [Line Items]
Goodwill impairment, measurement input	5.5	5.4		4.9
Measurement Input, EBITDA Multiple
Finite-Lived Intangible Assets [Line Items]
Goodwill impairment, measurement input	5.7	5.7
Measurement Input, EBITDA Multiple | Minimum
Finite-Lived Intangible Assets [Line Items]
Goodwill impairment, measurement input	4.8	5.6		4.9
Measurement Input, EBITDA Multiple | Maximum
Finite-Lived Intangible Assets [Line Items]
Goodwill impairment, measurement input	12.5	12.2		9.8
Consumer
Finite-Lived Intangible Assets [Line Items]
Goodwill impairment			$ 2,700,000,000		$ 2,700,000,000
Goodwill, impairment percent		44.00%
Small and Medium Business
Finite-Lived Intangible Assets [Line Items]
Goodwill, impairment percent		41.00%
Enterprise
Finite-Lived Intangible Assets [Line Items]
Goodwill, impairment percent	2.00%	53.00%
Wholesale
Finite-Lived Intangible Assets [Line Items]
Goodwill, impairment percent		46.00%
NA GAM
Finite-Lived Intangible Assets [Line Items]
Goodwill, impairment percent	46.00%	55.00%
EMEA
Finite-Lived Intangible Assets [Line Items]
Weighted average cost of capital, percentage	8.00%	6.80%
Cost of debt, after tax, percentage	2.90%	4.80%
Cost of equity, percentage	11.20%	8.10%
Goodwill, impairment percent		5.00%
LATAM
Finite-Lived Intangible Assets [Line Items]
Weighted average cost of capital, percentage	14.30%	10.00%
Cost of debt, after tax, percentage	6.90%	6.10%
Cost of equity, percentage	18.80%	12.50%
Goodwill, impairment percent	74.00%	63.00%
APAC
Finite-Lived Intangible Assets [Line Items]
Weighted average cost of capital, percentage	10.10%	9.00%
Cost of debt, after tax, percentage	3.90%	7.10%
Cost of equity, percentage	14.00%	10.20%
Goodwill, impairment percent	23.00%	38.00%