Investments - Held-to-maturity Securities by Type and Tenor (Detail) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	$ 68,510	$ 51,662
Fair Value	$ 66,515	$ 50,260
Weighted Average Yield	3.39%	2.99%
U.S. government obligations
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	$ 68,307	$ 51,499
Fair Value	$ 66,313	$ 50,100
Weighted Average Yield	3.38%	2.99%
U.S. government obligations | Less than 1 year
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	$ 16,020	$ 5,319
Fair Value	$ 15,859	$ 5,282
Weighted Average Yield	3.13%	2.98%
U.S. government obligations | 1 year to 5 years
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	$ 50,391	$ 45,154
Fair Value	$ 48,627	$ 43,852
Weighted Average Yield	3.45%	3.00%
U.S. government obligations | 5 years to 10 years
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	$ 1,896	$ 1,026
Fair Value	$ 1,827	$ 966
Weighted Average Yield	3.87%	2.89%
Securities backed by real estate
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	$ 203	$ 163
Fair Value	$ 202	$ 160
Weighted Average Yield	5.90%	3.24%
Securities backed by real estate | 1 year to 5 years
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	$ 3
Fair Value	$ 2
Weighted Average Yield	7.78%
Securities backed by real estate | 5 years to 10 years
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost		$ 2
Fair Value		$ 2
Weighted Average Yield		5.63%
Securities backed by real estate | Greater than 10 years
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	$ 200	$ 161
Fair Value	$ 200	$ 158
Weighted Average Yield	5.87%	3.18%