Investments (Portion Of Unrealized Gains And Losses On Equity Investments Held) (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Gain (Loss) on Investments [Line Items]
Realized investment gains (losses)			$ (24)	$ (1)
Equity and Trading securities [Member] | Gains (losses) on equity investments [Member]
Gain (Loss) on Investments [Line Items]
Realized investment gains (losses)	$ (18)	$ 3	(28)	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)	(1)	0	0	0
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)	$ (17)	$ 3	$ (28)	$ 5