Investments (Fair Value of Available-For-Sale Investments with Gross Unrealized Losses by Investment Type and Length of Time That Individual Securities Have Been in a Continuous Unrealized Loss Position) (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Debt Securities - held-to-maturity
Schedule of Investments [Line Items]
Less Than 12 Months, Fair Value	$ 24,899	$ 17,118
Less Than 12 Months, Gross Unrealized Losses	(1,750)	(237)
Greater Than 12 Months, Fair Value	12,320	886
Greater Than 12 Months, Gross Unrealized Losses	(1,914)	(37)
Total, Fair Value	37,219	18,004
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	(3,664)	(274)
U.S. Government and Agency Obligations [Member]
Schedule of Investments [Line Items]
Less Than 12 Months, Fair Value	2,007	1,976
Less Than 12 Months, Gross Unrealized Losses	(96)	(18)
Greater Than 12 Months, Fair Value	1,290	249
Greater Than 12 Months, Gross Unrealized Losses	(189)	(13)
Total, Fair Value	3,297	2,225
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	(285)	(31)
State and Municipal Obligations [Member]
Schedule of Investments [Line Items]
Less Than 12 Months, Fair Value	4,630	1,386
Less Than 12 Months, Gross Unrealized Losses	(288)	(19)
Greater Than 12 Months, Fair Value	1,178	31
Greater Than 12 Months, Gross Unrealized Losses	(191)	(1)
Total, Fair Value	5,808	1,417
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	(479)	(20)
Corporate Obligations [Member]
Schedule of Investments [Line Items]
Less Than 12 Months, Fair Value	13,003	9,357
Less Than 12 Months, Gross Unrealized Losses	(893)	(130)
Greater Than 12 Months, Fair Value	6,637	376
Greater Than 12 Months, Gross Unrealized Losses	(905)	(15)
Total, Fair Value	19,640	9,733
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	(1,798)	(145)
U.S. Agency Mortgage-Backed Securities [Member]
Schedule of Investments [Line Items]
Less Than 12 Months, Fair Value	3,561	3,078
Less Than 12 Months, Gross Unrealized Losses	(345)	(52)
Greater Than 12 Months, Fair Value	2,239	116
Greater Than 12 Months, Gross Unrealized Losses	(463)	(3)
Total, Fair Value	5,800	3,194
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	(808)	(55)
Non-U.S. Agency Mortgage-Backed Securities [Member]
Schedule of Investments [Line Items]
Less Than 12 Months, Fair Value	1,698	1,321
Less Than 12 Months, Gross Unrealized Losses	(128)	(18)
Greater Than 12 Months, Fair Value	976	114
Greater Than 12 Months, Gross Unrealized Losses	(166)	(5)
Total, Fair Value	2,674	1,435
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ (294)	$ (23)