Overview and Summary of Significant Accounting Policies - Changes on the Presentation of Operating Expenses (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Transaction expense	$ 6,790	$ 5,581	$ 4,419
Transaction and loan losses	1,380	1,274	1,011
Customer support and operations	1,615	1,407	1,265
Sales and marketing	1,401	1,314	1,142
Product development		0	0
Technology and development	2,085	1,831	1,740
General and administrative	1,711	1,541	1,258
Depreciation and amortization		0	0
Restructuring and other charges	71	309	132
Total operating expenses	$ 15,053	13,257	10,967
As Previously Reported ()
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Transaction expense		5,581	4,419
Transaction and loan losses		1,274	1,011
Customer support and operations		1,482	1,364
Sales and marketing		1,313	1,128
Product development		1,071	953
Technology and development		0	0
General and administrative		1,451	1,155
Depreciation and amortization		776	805
Restructuring and other charges		309	132
Total operating expenses		13,257	10,967
Adjustments
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Transaction expense		0	0
Transaction and loan losses		0	0
Customer support and operations		(75)	(99)
Sales and marketing		1	14
Product development		(1,071)	(953)
Technology and development		1,831	1,740
General and administrative		90	103
Depreciation and amortization		(776)	(805)
Restructuring and other charges		0	0
Total operating expenses		$ 0	$ 0