Business Segments (Summary Of Company's Segment Results) (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Segment Reporting Information [Line Items]
Revenues	[1]	$ 72	$ 100	$ 142
Net gains (losses) on financial instruments at fair value and foreign exchange		4	45	40
Net gains (losses) on extinguishment of debt		1	4	30
Revenues of consolidated VIEs		(70)	5	(23)
Inter-segment revenues	[2]	0	0	0
Total revenues		7	154	189
Losses and loss adjustment		177	38	350
Amortization of deferred acquisition costs and operating		92	76	97
Interest		210	179	163
Expenses of consolidated VIEs		12	9	24
Inter-segment expenses	[2]	0	0	0
Total expenses		491	302	634
Income (loss) from continuing operations before income taxes		(484)	(148)	(445)
Identifiable assets per segment		2,533	3,295
Assets held for sale		73	80
Total identifiable assets		2,606	3,375
Operating Segments [Member] | US Public Finance Insurance [Member]
Segment Reporting Information [Line Items]
Revenues	[1]	51	53	85
Net gains (losses) on financial instruments at fair value and foreign exchange		8	(47)	(2)
Net gains (losses) on extinguishment of debt		0	0	0
Revenues of consolidated VIEs		0	0	0
Inter-segment revenues	[2]	27	29	27
Total revenues		86	35	110
Losses and loss adjustment		170	143	227
Amortization of deferred acquisition costs and operating		7	8	17
Interest		0	0	0
Expenses of consolidated VIEs		0	0	0
Inter-segment expenses	[2]	40	44	45
Total expenses		217	195	289
Income (loss) from continuing operations before income taxes		(131)	(160)	(179)
Identifiable assets per segment		1,742	2,491
Assets held for sale		0	0
Total identifiable assets		1,742	2,491
Operating Segments [Member] | Corporate Operations [Member]
Segment Reporting Information [Line Items]
Revenues	[1]	(12)	8	13
Net gains (losses) on financial instruments at fair value and foreign exchange		8	99	56
Net gains (losses) on extinguishment of debt		1	5	30
Revenues of consolidated VIEs		0	0	0
Inter-segment revenues	[2]	54	55	67
Total revenues		51	167	166
Losses and loss adjustment		0	0	0
Amortization of deferred acquisition costs and operating		74	55	71
Interest		55	56	56
Expenses of consolidated VIEs		0	0	0
Inter-segment expenses	[2]	24	23	22
Total expenses		153	134	149
Income (loss) from continuing operations before income taxes		(102)	33	17
Identifiable assets per segment		755	645
Assets held for sale		0	0
Total identifiable assets		755	645
Operating Segments [Member] | International And Structured Finance Insurance [Member]
Segment Reporting Information [Line Items]
Revenues	[1]	33	39	44
Net gains (losses) on financial instruments at fair value and foreign exchange		(12)	(7)	(14)
Net gains (losses) on extinguishment of debt		0	0	0
Revenues of consolidated VIEs		(70)	5	(23)
Inter-segment revenues	[2]	6	9	12
Total revenues		(43)	46	19
Losses and loss adjustment		7	(105)	123
Amortization of deferred acquisition costs and operating		10	12	9
Interest		155	124	107
Expenses of consolidated VIEs		12	9	24
Inter-segment expenses	[2]	23	27	38
Total expenses		207	67	301
Income (loss) from continuing operations before income taxes		(250)	(21)	(282)
Identifiable assets per segment		974	1,132
Assets held for sale		0	0
Total identifiable assets		974	1,132
Intersegment Elimination [Member]
Segment Reporting Information [Line Items]
Revenues	[1]	0	0	0
Net gains (losses) on financial instruments at fair value and foreign exchange		0	0	0
Net gains (losses) on extinguishment of debt		0	(1)	0
Revenues of consolidated VIEs		0	0	0
Inter-segment revenues	[2]	(87)	(93)	(106)
Total revenues		(87)	(94)	(106)
Losses and loss adjustment		0	0	0
Amortization of deferred acquisition costs and operating		1	1	0
Interest		0	(1)	0
Expenses of consolidated VIEs		0	0	0
Inter-segment expenses	[2]	(87)	(94)	(105)
Total expenses		(86)	(94)	(105)
Income (loss) from continuing operations before income taxes		(1)	0	$ (1)
Identifiable assets per segment	[3]	(938)	(973)
Assets held for sale		0	0
Total identifiable assets		$ (938)	$ (973)

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