Investments and Cash - Roll Forward of Credit Losses in the Investment Portfolio (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Roll Forward of Credit Losses in the Investment Portfolio
Balance, beginning of period	$ 65	$ 42	$ 78
Credit loss expense	0	7	4
Additions for purchases of securities accounted for as purchased financial assets with credit deterioration	0	2	0
Debt Securities, Available-for-Sale, Excluding Accrued Interest, Allowance for Credit Loss, Not to Sell before Recovery, Credit Loss, Previously Recorded, Expense (Reversal)	12	14	2
Reductions for securities sold and other settlements	0	0	(42)
Debt Securities, Available-for-Sale, Allowance for Credit Loss, Excluding Accrued Interest, Ending Balance	$ 77	$ 65	$ 42