Business Segments (Summary Of Company's Segment Results) (Detail) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2023		Mar. 31, 2022		Dec. 31, 2022
Segment Reporting Information [Line Items]
Revenues		$ 33	[1]	$ 27	[2]
Net gains (losses) on financial instruments at fair value and foreign exchange		(13)		17
Revenues of consolidated VIEs		(18)		(4)
Inter-segment revenues	[3]	0		0
Total revenues		2		40
Losses and loss adjustment		6		49
Amortization of deferred acquisition costs and operating		24		21
Interest		51		41
Expenses of consolidated VIEs		4		2
Inter-segment expenses	[3]	0		0
Total expenses		85		113
Income (loss) from continuing operations before income taxes		(83)		(73)
Identifiable assets per segment		3,234
Assets held for sale		83
Total identifiable assets		3,317				$ 3,375
Operating Segments [Member] | US Public Finance Insurance [Member]
Segment Reporting Information [Line Items]
Revenues		22	[1]	20	[2]
Net gains (losses) on financial instruments at fair value and foreign exchange		2		(16)
Revenues of consolidated VIEs		0		0
Inter-segment revenues	[3]	7		8
Total revenues		31		12
Losses and loss adjustment		0		87
Amortization of deferred acquisition costs and operating		2		3
Interest		0		0
Expenses of consolidated VIEs		0		0
Inter-segment expenses	[3]	12		13
Total expenses		14		103
Income (loss) from continuing operations before income taxes		17		(91)
Identifiable assets per segment		2,472
Assets held for sale		0
Total identifiable assets		2,472
Operating Segments [Member] | Corporate Operations [Member]
Segment Reporting Information [Line Items]
Revenues		5	[1]	2	[2]
Net gains (losses) on financial instruments at fair value and foreign exchange		(12)		39
Revenues of consolidated VIEs		0		0
Inter-segment revenues	[3]	14		17
Total revenues		7		58
Losses and loss adjustment		0		0
Amortization of deferred acquisition costs and operating		18		15
Interest		14		14
Expenses of consolidated VIEs		0		0
Inter-segment expenses	[3]	6		6
Total expenses		38		35
Income (loss) from continuing operations before income taxes		(31)		23
Identifiable assets per segment		638
Assets held for sale		0
Total identifiable assets		638
Operating Segments [Member] | International And Structured Finance Insurance [Member]
Segment Reporting Information [Line Items]
Revenues		6	[1]	5	[2]
Net gains (losses) on financial instruments at fair value and foreign exchange		(3)		(6)
Revenues of consolidated VIEs		(18)		(4)
Inter-segment revenues	[3]	2		3
Total revenues		(13)		(2)
Losses and loss adjustment		6		(38)
Amortization of deferred acquisition costs and operating		3		3
Interest		37		27
Expenses of consolidated VIEs		4		2
Inter-segment expenses	[3]	6		9
Total expenses		56		3
Income (loss) from continuing operations before income taxes		(69)		(5)
Identifiable assets per segment		1,055
Assets held for sale		0
Total identifiable assets		1,055
Intersegment Elimination [Member]
Segment Reporting Information [Line Items]
Revenues		0	[1]	0	[2]
Net gains (losses) on financial instruments at fair value and foreign exchange		0		0
Revenues of consolidated VIEs		0		0
Inter-segment revenues	[3]	(23)		(28)
Total revenues		(23)		(28)
Losses and loss adjustment		0		0
Amortization of deferred acquisition costs and operating		1		0
Interest		0		0
Expenses of consolidated VIEs		0		0
Inter-segment expenses	[3]	(24)		(28)
Total expenses		(23)		(28)
Income (loss) from continuing operations before income taxes		0		$ 0
Identifiable assets per segment		(931)
Assets held for sale		0
Total identifiable assets	[4]	$ (931)

[1] Consists of net premiums earned, net investment income and net realized investment gains (losses).

[2] Consists of net premiums earned, net investment income, net realized investment gains (losses), fees and reimbursements and other net realized gains (losses).

[3] Primarily represents intercompany service charges and intercompany net investment income and expenses.

[4] Consists principally of intercompany reinsurance balances.