Accumulated Other Comprehensive Income (Loss) (AOCI) (Components of Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive income (loss), net of tax, Beginning Balance	$ (92)
Change in unrealized gains (losses) on debt securities	(496)
Change in foreign currency translation adjustment	1
Amortization of net actuarial loss	2
Tax effect	124	$ 30
Accumulated other comprehensive income (loss), net of tax, Ending Balance	(461)
Unrealized Gains (Losses) on Debt Securities
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive income (loss), debt securities, available-for-sale, adjustment, after tax, Beginning Balance	29
Change in unrealized gains (losses) on debt securities	(496)
Tax effect	125	32
Accumulated other comprehensive income (loss), debt securities, available-for-sale, adjustment, after tax, Ending Balance	(342)
Foreign Currency Translation Adjustment
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive income (loss), foreign currency translation adjustment, net of tax, Beginning Balance	(39)
Change in foreign currency translation adjustment	1
Tax effect	0	$ (1)
Accumulated other comprehensive income (loss), foreign currency translation adjustment, net of tax, Ending Balance	(38)
Pension Benefit Adjustment
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive (income) Loss, defined benefit plan, after Tax, Beginning Balance	(82)
Amortization of net actuarial loss	2
Tax effect	(1)
Accumulated other comprehensive (income) Loss, defined benefit plan, after Tax, Ending Balance	$ (81)