Investments - Available-for-Sale Securities by Tenor (Detail) - USD ($) $ in Millions	Sep. 30, 2022	Dec. 31, 2021
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 52,019	$ 49,593
Fair Value	$ 48,125	$ 48,932
Weighted Average Yield	0.64%	0.52%
U.S.
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 49,549	$ 46,900
Fair Value	$ 46,196	$ 46,322
Weighted Average Yield	0.65%	0.53%
Non-U.S.
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 2,470	$ 2,693
Fair Value	$ 1,929	$ 2,610
Weighted Average Yield	0.40%	0.33%
Less than 1 year | U.S.
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 2,353	$ 25
Fair Value	$ 2,295	$ 25
Weighted Average Yield	0.24%	0.12%
1 year to 5 years | U.S.
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 46,366	$ 41,536
Fair Value	$ 43,125	$ 41,066
Weighted Average Yield	0.65%	0.47%
1 year to 5 years | Non-U.S.
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 9
Fair Value	$ 9
Weighted Average Yield	0.28%
5 years to 10 years | U.S.
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 830	$ 5,337
Fair Value	$ 776	$ 5,229
Weighted Average Yield	2.14%	0.92%
5 years to 10 years | Non-U.S.
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 2,461	$ 2,693
Fair Value	$ 1,920	$ 2,610
Weighted Average Yield	0.40%	0.33%
Greater than 10 years | U.S.
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		$ 2
Fair Value		$ 2
Weighted Average Yield		2.00%