Investments (Portion Of Unrealized Gains And Losses On Equity Investments Held) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Gain (Loss) on Investments [Line Items]
Realized investment gains (losses)	$ (41)	$ 5	$ 48
Equity and Trading securities [Member] | Net gains and (losses) recognized during the period on equity securities [Member]
Gain (Loss) on Investments [Line Items]
Realized investment gains (losses)	(21)	6	3
Equity and Trading securities [Member] | Net gains and (losses) recognized during the period on equity securities sold during the period [Member]
Gain (Loss) on Investments [Line Items]
Realized investment gains (losses)	(6)	1	(1)
Equity and Trading securities [Member] | Unrealized gains and (losses) recognized during the period on equity securities still held at the reporting date [Member]
Gain (Loss) on Investments [Line Items]
Realized investment gains (losses)	$ (15)	$ 5	$ 4