Acquisitions and Dispositions - Narrative (Details) - USD ($) $ in Millions			3 Months Ended		9 Months Ended		12 Months Ended
	Feb. 18, 2020	Jul. 29, 2019	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Jul. 29, 2020	Jun. 30, 2020	Dec. 31, 2019
Business Acquisition [Line Items]
Goodwill			$ 35,908		$ 35,908				$ 36,038
Tax expense			124	$ 53	176	$ 144
Net adjustment to noncontrolling interests from dissolution			762		762
Tax expense					112
Investment			2,772		2,772				$ 2,720
Additional Paid-In Capital
Business Acquisition [Line Items]
Net adjustment to noncontrolling interests from dissolution			36		36
Banc of America Merchant Services | Corporate joint venture
Business Acquisition [Line Items]
Percentage of interest in joint venture								51.00%
Banc of America Merchant Services Joint Venture
Business Acquisition [Line Items]
Noncontrolling interest, period increase (decrease)			$ 726
Banc of America Merchant Services Joint Venture | Bank Of America
Business Acquisition [Line Items]
Processing and other support services agreement, term (in years)			5 years
Banc of America Merchant Services Joint Venture | Corporate joint venture | Bank Of America
Business Acquisition [Line Items]
Pre-tax gain			$ 36
Tax expense			13
Revaluation/Remeasurement gain			700
Additional consideration gain			24
Investment Services Business
Business Acquisition [Line Items]
Controlling interest sold (as a percent)	60.00%
Percentage of interest owned in affiliate	40.00%
Investment			178		178
Disposal Group, Disposed of by Sale
Business Acquisition [Line Items]
Revaluation/Remeasurement gain	$ 176
Consideration from sale of business	578
Tax expense	$ 112
Disposal Group, Disposed of by Sale | Investment Services Business
Business Acquisition [Line Items]
Controlling interest sold (as a percent)	60.00%
Pre-tax gain on sale	$ 428
First Data
Business Acquisition [Line Items]
Percentage of business acquired		100.00%
Entity shares issued per acquiree share (in shares)		0.303
Repayment of First Data debt		$ 16,414
Increase in goodwill							$ 304
Measurement period adjustments, reduction in intangible assets							155
Measurement period adjustments, reduction in noncontrolling interests							126
Measurement period adjustments, reduction in property and equipment							25
Measurement period adjustments, increase in accounts payable and accrued expenses							37
Measurement period adjustments, reduction in investments in unconsolidated affiliates							23
Measurement period adjustments, increase in other long-term liabilities							21
Measurement period adjustments, increase in deferred tax liabilities							$ 178
Transaction expenses incurred				47		172
Payments for acquisitions of businesses		46,475
Goodwill		$ 30,811
First Data | Common Shares
Business Acquisition [Line Items]
Shares issued to acquire First Data (in shares)		286,000,000
First Data | Equity Awards
Business Acquisition [Line Items]
Shares issued to acquire First Data (in shares)		15,000,000
First Data | Selling, General and Administrative Expenses
Business Acquisition [Line Items]
Transaction expenses incurred				45		74
First Data | Debt Financing Activities
Business Acquisition [Line Items]
Transaction expenses incurred				$ 2		$ 98
Other Acquisitions
Business Acquisition [Line Items]
Goodwill, expected tax deductible amount			35		35
Payments for acquisitions of businesses					167
Acquired cash					2
Earn-out provisions estimated value			45		45
Goodwill			82		82
Net assumed liabilities			6		6
Other Acquisitions | Software And Customer Intangible Assets
Business Acquisition [Line Items]
Intangible assets			56		56
Other Acquisitions | Residual Buyout Intangible Assets
Business Acquisition [Line Items]
Intangible assets			$ 35		$ 35