Overview and Summary of Significant Accounting Policies - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Allowance for negative customer balances, threshold period past due, writeoff	120 days
Allowance for negative customer balances	$ 276	$ 263
Other current assets
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Accrued interest receivable	45	54
Accrued Expenses and Other Current Liabilities
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Allowance for transaction losses	$ 120	$ 136
Consumer Receivables
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Projected loss rate period	7 years
Merchant Receivables | Minimum
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Projected loss rate period	2 years 6 months
Merchant Receivables | Maximum
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Projected loss rate period	3 years 6 months