Investments (Portion Of Unrealized Gains And Losses On Equity Investments Held) (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Gain (Loss) on Investments [Line Items]
Realized investment gains (losses)			$ (0)	$ (6)
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)	$ 2	$ 4	0	1
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	2
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)	$ 1	$ 4	$ (1)	$ (1)