Income Taxes - Summary of Income Tax Expense Allocated Based on Separate Tax Return Basis (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Current income taxes: Federal taxes	$ 79	$ 71	$ 47
Current income taxes: State taxes	4	5	4
Total current income taxes	83	76	51
Deferred income taxes: Federal taxes	12	(20)	30
Deferred income taxes: State taxes	3	1	3
Total deferred income taxes	15	(19)	33
Total income taxes	$ 98	$ 57	$ 84