Investments - Held-to-maturity Securities by Type and Tenor (Detail) - USD ($) $ in Millions	Sep. 30, 2022	Dec. 31, 2021
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	$ 48,549	$ 4,699
Fair Value	$ 47,020	$ 4,873
Weighted Average Yield	2.75%	2.13%
U.S. government obligations
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	$ 48,383	$ 4,054
Fair Value	$ 46,858	$ 4,200
Weighted Average Yield	2.75%	2.30%
U.S. government obligations | Less than 1 year
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	$ 5,920
Fair Value	$ 5,908
Weighted Average Yield	2.25%
U.S. government obligations | 1 year to 5 years
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	$ 40,254	$ 4,054
Fair Value	$ 38,816	$ 4,200
Weighted Average Yield	2.79%	2.30%
U.S. government obligations | 5 years to 10 years
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	$ 2,209
Fair Value	$ 2,134
Weighted Average Yield	3.41%
Securities backed by real estate
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	$ 166	$ 645
Fair Value	$ 162	$ 673
Weighted Average Yield	1.84%	1.04%
Securities backed by real estate | 5 years to 10 years
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	$ 2	$ 3
Fair Value	$ 2	$ 3
Weighted Average Yield	4.39%	2.78%
Securities backed by real estate | Greater than 10 years
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	$ 164	$ 642
Fair Value	$ 160	$ 670
Weighted Average Yield	1.79%	1.03%