Investments - Fair Values (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Debt Securities, Available-for-sale [Line Items]
Amortized cost, net	$ 17,307	$ 21,522
Gross unrealized, gains	760	2,427
Gross unrealized, losses	(130)	(42)
Fair value	17,937	23,907
U.S. government and agencies
Debt Securities, Available-for-sale [Line Items]
Amortized cost, net	476	1,060
Gross unrealized, gains	18	45
Gross unrealized, losses	(8)	0
Fair value	486	1,105
Municipal
Debt Securities, Available-for-sale [Line Items]
Amortized cost, net	755	1,650
Gross unrealized, gains	66	357
Gross unrealized, losses	(4)	0
Fair value	817	2,007
Corporate
Debt Securities, Available-for-sale [Line Items]
Amortized cost, net	14,095	18,287
Gross unrealized, gains	656	2,009
Gross unrealized, losses	(114)	(40)
Fair value	14,637	20,256
Foreign government
Debt Securities, Available-for-sale [Line Items]
Amortized cost, net	11	91
Gross unrealized, gains	1	5
Gross unrealized, losses	0	0
Fair value	12	96
ABS
Debt Securities, Available-for-sale [Line Items]
Amortized cost, net	1,193	420
Gross unrealized, gains	17	6
Gross unrealized, losses	(3)	(2)
Fair value	1,207	424
MBS
Debt Securities, Available-for-sale [Line Items]
Amortized cost, net	777	14
Gross unrealized, gains	2	5
Gross unrealized, losses	(1)	0
Fair value	$ 778	$ 19

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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