Investments (Portion Of Unrealized Gains And Losses On Equity Investments Held) (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Gain (Loss) on Investments [Line Items]
Realized investment gains (losses)			$ (3)	$ (10)
Equity and Trading securities [Member] \| Net gains (losses) recognized during the period on equity and trading securities [Member]
Gain (Loss) on Investments [Line Items]
Realized investment gains (losses)	$ (56)	$ 2	(58)	3
Equity and Trading securities [Member] \| Net gains (losses) recognized during the period on equity and trading securities sold during the period [Member]
Gain (Loss) on Investments [Line Items]
Realized investment gains (losses)	1	0	1	0
Equity and Trading securities [Member] \| Unrealized gains (losses) recognized during the period on equity and trading securities still held at the reporting date [Member]
Gain (Loss) on Investments [Line Items]
Realized investment gains (losses)	$ (57)	$ 2	$ (59)	$ 3