Investments (Summary of Amount of Gross Unrealized Losses for Debt Securities and Estimated Fair Value) (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Gross unrealized losses
Available-for-sale, less than 12 Months	$ 1	$ 73
Available-for-sale, 12 Months or more	1,557	1,386
Available-for-sale, total	1,558	1,459
Estimated fair value
Available-for-sale, less than 12 Months	56	550
Available-for-sale, 12 months or more	9,027	9,373
Available-for-sale, total	9,083	9,923
Municipal securities
Gross unrealized losses
Available-for-sale, less than 12 Months	1	2
Available-for-sale, 12 Months or more	90	65
Available-for-sale, total	91	67
Estimated fair value
Available-for-sale, less than 12 Months	25	229
Available-for-sale, 12 months or more	1,143	1,061
Available-for-sale, total	1,168	1,290
U.S. Treasury securities
Gross unrealized losses
Available-for-sale, less than 12 Months	0	0
Available-for-sale, 12 Months or more	109	93
Available-for-sale, total	109	93
Estimated fair value
Available-for-sale, less than 12 Months	10	0
Available-for-sale, 12 months or more	293	308
Available-for-sale, total	303	308
Agency securities
Gross unrealized losses
Available-for-sale, less than 12 Months	0	0
Available-for-sale, 12 Months or more	32	33
Available-for-sale, total	32	33
Estimated fair value
Available-for-sale, less than 12 Months	1	5
Available-for-sale, 12 months or more	458	605
Available-for-sale, total	459	610
Agency guaranteed mortgage-backed securities
Gross unrealized losses
Available-for-sale, less than 12 Months	0	71
Available-for-sale, 12 Months or more	1,302	1,168
Available-for-sale, total	1,302	1,239
Estimated fair value
Available-for-sale, less than 12 Months	19	312
Available-for-sale, 12 months or more	6,681	6,902
Available-for-sale, total	6,700	7,214
Small Business Administration loan-backed securities
Gross unrealized losses
Available-for-sale, less than 12 Months	0	0
Available-for-sale, 12 Months or more	23	25
Available-for-sale, total	23	25
Estimated fair value
Available-for-sale, less than 12 Months	1	4
Available-for-sale, 12 months or more	438	484
Available-for-sale, total	439	488
Other
Gross unrealized losses
Available-for-sale, less than 12 Months	0	0
Available-for-sale, 12 Months or more	1	2
Available-for-sale, total	1	2
Estimated fair value
Available-for-sale, less than 12 Months	0	0
Available-for-sale, 12 months or more	14	13
Available-for-sale, total	$ 14	$ 13

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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