Debt Securities (Gross Unrealized Losses on Investments in Debt Securities) (Detail) - USD ($) $ in Millions	Jun. 30, 2022	Dec. 31, 2021
Schedule Of Available For Sale Securities [Line Items]
Estimated fair value, Less than 12 months	$ 7,199	$ 5,739
Unrealized losses, Less than 12 months	(704)	(80)
Estimated fair value, 12 months or longer	633	33
Unrealized losses, 12 months or longer	(108)	(2)
Estimated fair value, Total	7,832	5,772
Unrealized losses, Total	(812)	(82)
U.S. Treasury bonds
Schedule Of Available For Sale Securities [Line Items]
Estimated fair value, Less than 12 months	114	76
Unrealized losses, Less than 12 months	(7)	(1)
Estimated fair value, 12 months or longer	10
Unrealized losses, 12 months or longer	(1)
Estimated fair value, Total	124	76
Unrealized losses, Total	(8)	(1)
Municipal bonds
Schedule Of Available For Sale Securities [Line Items]
Estimated fair value, Less than 12 months	1,213	684
Unrealized losses, Less than 12 months	(136)	(17)
Estimated fair value, 12 months or longer	58
Unrealized losses, 12 months or longer	(13)
Estimated fair value, Total	1,271	684
Unrealized losses, Total	(149)	(17)
Foreign government bonds
Schedule Of Available For Sale Securities [Line Items]
Estimated fair value, Less than 12 months	136	103
Unrealized losses, Less than 12 months	(10)	(1)
Estimated fair value, 12 months or longer	33	33
Unrealized losses, 12 months or longer	(7)	(2)
Estimated fair value, Total	169	136
Unrealized losses, Total	(17)	(3)
Governmental agency bonds
Schedule Of Available For Sale Securities [Line Items]
Estimated fair value, Less than 12 months	125	73
Unrealized losses, Less than 12 months	(11)	(1)
Estimated fair value, 12 months or longer	4
Unrealized losses, 12 months or longer	(1)
Estimated fair value, Total	129	73
Unrealized losses, Total	(12)	(1)
Governmental agency mortgage-backed securities
Schedule Of Available For Sale Securities [Line Items]
Estimated fair value, Less than 12 months	4,304	4,036
Unrealized losses, Less than 12 months	(414)	(47)
Estimated fair value, 12 months or longer	477
Unrealized losses, 12 months or longer	(78)
Estimated fair value, Total	4,781	4,036
Unrealized losses, Total	(492)	(47)
U.S. corporate debt securities
Schedule Of Available For Sale Securities [Line Items]
Estimated fair value, Less than 12 months	887	533
Unrealized losses, Less than 12 months	(88)	(9)
Estimated fair value, 12 months or longer	30
Unrealized losses, 12 months or longer	(5)
Estimated fair value, Total	917	533
Unrealized losses, Total	(93)	(9)
Foreign corporate debt securities
Schedule Of Available For Sale Securities [Line Items]
Estimated fair value, Less than 12 months	420	234
Unrealized losses, Less than 12 months	(38)	(4)
Estimated fair value, 12 months or longer	21
Unrealized losses, 12 months or longer	(3)
Estimated fair value, Total	441	234
Unrealized losses, Total	$ (41)	$ (4)

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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