Summary of Significant Accounting Policies Accounts Payable (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Payables and Accruals [Abstract]
Accounts Payable	$ 191	$ 125
Accrued Salaries, Current	71	62
Accrued Exchange Fee Rebate, Current	45	44
Taxes Payable, Current	12	15
Operating Lease, Liability, Current	7	8
Loss Contingency, Accrual, Current	1	1
Other Accrued Liabilities, Current	11	13
Accounts payable and accrued liabilities	338	268
Unpaid capital expenditures	$ 46	$ 16	$ 15