Summary of Significant Accounting Policies Accounts Payable (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Payables and Accruals [Abstract]
Accounts Payable	$ 141	$ 178
Accrued Salaries, Current	57	66
Accrued Exchange Fee Rebate, Current	37	46
Taxes Payable, Current	3	10
Operating Lease, Liability, Current	6	8
Other Accrued Liabilities, Current	10	9
Accounts payable and accrued liabilities	254	317
Unpaid capital expenditures	15	48	$ 46
Advertising Expense	$ 25	$ 28	$ 24
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	Accounts payable and accrued liabilities	Accounts payable and accrued liabilities