Investments (Portion Of Unrealized Gains And Losses On Equity Investments Held) (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Gain (Loss) on Investments [Line Items]
Realized investment gains (losses)			$ (37)	$ 1
Equity and Trading securities [Member] | Gains (losses) on equity investments [Member]
Gain (Loss) on Investments [Line Items]
Realized investment gains (losses)	$ (3)	$ 0	(31)	5
Equity and Trading securities [Member] | Gains (losses) on equity investments sold during the period [Member]
Gain (Loss) on Investments [Line Items]
Realized investment gains (losses)	(6)	1	(6)	1
Equity and Trading securities [Member] | Gains (losses) on equity investments still held at the end of the period [Member]
Gain (Loss) on Investments [Line Items]
Realized investment gains (losses)	$ 3	$ (1)	$ (25)	$ 4