Business Segments (Summary Of Company's Segment Results) (Detail) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Segment Reporting Information [Line Items]
Revenues	[1]	$ 33	$ 33
Net gains (losses) on financial instruments at fair value and foreign exchange		4	(13)
Net gains (losses) on extinguishment of debt		1	0
Revenues of consolidated VIEs		(25)	(18)
Inter-segment revenues	[2]	0	0
Total revenues		13	2
Losses and loss adjustment		18	6
Amortization of deferred acquisition costs and operating		26	24
Interest		52	51
Expenses of consolidated VIEs		4	4
Inter-segment expenses	[2]	0	0
Total expenses		100	85
Income (loss) from continuing operations before income taxes		(87)	(83)
Identifiable assets per segment		2,414
Assets held for sale		74
Total identifiable assets		2,488		$ 2,606
Operating Segments [Member] | US Public Finance Insurance [Member]
Segment Reporting Information [Line Items]
Revenues	[1]	19	22
Net gains (losses) on financial instruments at fair value and foreign exchange		1	2
Net gains (losses) on extinguishment of debt		0
Revenues of consolidated VIEs		0	0
Inter-segment revenues	[2]	6	7
Total revenues		26	31
Losses and loss adjustment		22	0
Amortization of deferred acquisition costs and operating		2	2
Interest		0	0
Expenses of consolidated VIEs		0	0
Inter-segment expenses	[2]	11	12
Total expenses		35	14
Income (loss) from continuing operations before income taxes		(9)	17
Identifiable assets per segment		1,720
Assets held for sale		0
Total identifiable assets		1,720
Operating Segments [Member] | Corporate Operations [Member]
Segment Reporting Information [Line Items]
Revenues	[1]	7	5
Net gains (losses) on financial instruments at fair value and foreign exchange		8	(12)
Net gains (losses) on extinguishment of debt		1
Revenues of consolidated VIEs		0	0
Inter-segment revenues	[2]	15	14
Total revenues		31	7
Losses and loss adjustment		0	0
Amortization of deferred acquisition costs and operating		21	18
Interest		13	14
Expenses of consolidated VIEs		0	0
Inter-segment expenses	[2]	6	6
Total expenses		40	38
Income (loss) from continuing operations before income taxes		(9)	(31)
Identifiable assets per segment		710
Assets held for sale		0
Total identifiable assets		710
Operating Segments [Member] | International And Structured Finance Insurance [Member]
Segment Reporting Information [Line Items]
Revenues	[1]	7	6
Net gains (losses) on financial instruments at fair value and foreign exchange		(5)	(3)
Net gains (losses) on extinguishment of debt		0
Revenues of consolidated VIEs		(25)	(18)
Inter-segment revenues	[2]	1	2
Total revenues		(22)	(13)
Losses and loss adjustment		(4)	6
Amortization of deferred acquisition costs and operating		2	3
Interest		39	37
Expenses of consolidated VIEs		4	4
Inter-segment expenses	[2]	6	6
Total expenses		47	56
Income (loss) from continuing operations before income taxes		(69)	(69)
Identifiable assets per segment		928
Assets held for sale		0
Total identifiable assets		928
Intersegment Elimination [Member]
Segment Reporting Information [Line Items]
Revenues	[1]	0	0
Net gains (losses) on financial instruments at fair value and foreign exchange		0	0
Net gains (losses) on extinguishment of debt		0
Revenues of consolidated VIEs		0	0
Inter-segment revenues	[2]	(22)	(23)
Total revenues		(22)	(23)
Losses and loss adjustment		0	0
Amortization of deferred acquisition costs and operating		1	1
Interest		0	0
Expenses of consolidated VIEs		0	0
Inter-segment expenses	[2]	(23)	(24)
Total expenses		(22)	(23)
Income (loss) from continuing operations before income taxes		0	$ 0
Identifiable assets per segment	[3]	(944)
Assets held for sale		0
Total identifiable assets		$ (944)

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

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

[3] Consists principally of intercompany reinsurance balances.