Summary of Significant Accounting Policies - Allowance for Merchant Credit Losses (Details) - Merchant credit losses - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Loss Contingencies [Line Items]
Aggregate merchant credit losses incurred	$ 41	$ 113	$ 40
Collateral held	2,200	1,200
Loss contingency accrual	$ 42	$ 59