Summary of Significant Accounting Policies - Revenue Recognition (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2025	Dec. 31, 2024
Disaggregation of Revenue [Line Items]
Prepaid merchant bookings	$ 481	$ 319
Deferred merchant bookings	13,415	8,517
Deferred revenue	167	164
Deferred Merchant Bookings
Disaggregation of Revenue [Line Items]
Deferred merchant bookings	12,300	7,600
Deferred merchant bookings recognized during period	5,700
Revenue recognized during period	807
Deferred Loyalty Rewards
Disaggregation of Revenue [Line Items]
Deferred merchant bookings	1,100	937
Revenue recognized during period	431
Deferred Revenue
Disaggregation of Revenue [Line Items]
Revenue recognized during period	104
Deferred revenue	$ 167	$ 164