Equity Securities - (Summary of Investments in Marketable Equity Securities) (Detail) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Schedule Of Trading Securities And Other Trading Assets [Line Items]
Equity securities, Cost	$ 339	$ 435
Equity securities, Unrealized gains (losses)	(59)	222
Equity securities, Estimated fair value	280	657
Common Stock
Schedule Of Trading Securities And Other Trading Assets [Line Items]
Equity securities, Cost	324	418
Equity securities, Unrealized gains (losses)	(55)	222
Equity securities, Estimated fair value	269	640
Preferred Stock
Schedule Of Trading Securities And Other Trading Assets [Line Items]
Equity securities, Cost	15	17
Equity securities, Unrealized gains (losses)	(4)	0
Equity securities, Estimated fair value	$ 11	$ 17