Available for Sale Debt Securities Reconciliation (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 11,580	$ 9,912
Unrealized Gains	1	6
Unrealized Losses	834	834
Fair Value	10,747	9,084
Taxable bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	11,373	9,705
Unrealized Gains	1	6
Unrealized Losses	829	830
Fair Value	10,545	8,881
Tax exempt bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	20	37
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	20	37
Restricted investments [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	187	170
Unrealized Gains	0	0
Unrealized Losses	5	4
Fair Value	$ 182	$ 166