Business Segments (Summary Of Company's Segment Results) (Detail) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Segment Reporting Information [Line Items]
Revenues	[1]	$ 17	$ 23	$ 89	$ 53
Net gains (losses) on financial instruments at fair value and foreign exchange		21	25	20	51
Revenues of consolidated VIEs		(30)	(31)	(72)	(11)
Inter-segment revenues	[2]	0	0	0	0
Total revenues		8	17	38	97
Losses and loss adjustment		123	(12)	158	57
Amortization of deferred acquisition costs and operating		16	16	60	49
Interest		53	46	157	130
Expenses of consolidated VIEs		1	2	9	5
Inter-segment expenses	[2]	0	0	0	0
Total expenses		193	52	384	241
Income (loss) from continuing operations before income taxes		(185)	(35)	(346)	(144)
Identifiable assets per segment		2,916		2,916
Net gains (losses) on extinguishment of debt		0	0	1	4
Assets held for sale		74		74
Total identifiable assets		2,990		2,990		$ 3,375
Operating Segments [Member] | US Public Finance Insurance [Member]
Segment Reporting Information [Line Items]
Revenues	[1]	15	17	56	24
Net gains (losses) on financial instruments at fair value and foreign exchange		(1)	(6)	1	(43)
Revenues of consolidated VIEs		0	0	0	0
Inter-segment revenues	[2]	6	6	20	20
Total revenues		20	17	77	1
Losses and loss adjustment		143	16	169	152
Amortization of deferred acquisition costs and operating		0	2	4	6
Interest		0	0	0	0
Expenses of consolidated VIEs		0	0	0	0
Inter-segment expenses	[2]	11	10	31	33
Total expenses		154	28	204	191
Income (loss) from continuing operations before income taxes		(134)	(11)	(127)	(190)
Identifiable assets per segment		2,379		2,379
Net gains (losses) on extinguishment of debt				0	0
Assets held for sale		0		0
Total identifiable assets		2,379		2,379
Operating Segments [Member] | Corporate Operations [Member]
Segment Reporting Information [Line Items]
Revenues	[1]	(1)	(3)	6	3
Net gains (losses) on financial instruments at fair value and foreign exchange		23	35	25	111
Revenues of consolidated VIEs		0	0		0
Inter-segment revenues	[2]	13	12	41	43
Total revenues		35	44	73	162
Losses and loss adjustment		0	0	0	0
Amortization of deferred acquisition costs and operating		11	12	47	35
Interest		13	14	41	42
Expenses of consolidated VIEs		0	0	0	0
Inter-segment expenses	[2]	7	5	18	17
Total expenses		31	31	106	94
Income (loss) from continuing operations before income taxes		4	13	(33)	68
Identifiable assets per segment		564		564
Net gains (losses) on extinguishment of debt				0	5
Assets held for sale		0		0
Total identifiable assets		564		564
Operating Segments [Member] | International And Structured Finance Insurance [Member]
Segment Reporting Information [Line Items]
Revenues	[1]	4	9	28	26
Net gains (losses) on financial instruments at fair value and foreign exchange		(1)	(4)	(6)	(17)
Revenues of consolidated VIEs		(30)	(31)	(72)	(11)
Inter-segment revenues	[2]	1	2	4	7
Total revenues		(26)	(24)	(46)	5
Losses and loss adjustment		(20)	(28)	(11)	(95)
Amortization of deferred acquisition costs and operating		3	2	8	8
Interest		40	32	116	88
Expenses of consolidated VIEs		1	2	9	5
Inter-segment expenses	[2]	5	6	17	20
Total expenses		29	14	139	26
Income (loss) from continuing operations before income taxes		(55)	(38)	(185)	(21)
Identifiable assets per segment		978		978
Net gains (losses) on extinguishment of debt				0	0
Assets held for sale		0		0
Total identifiable assets		978		978
Intersegment Elimination [Member]
Segment Reporting Information [Line Items]
Revenues	[1]	(1)	0	(1)	0
Net gains (losses) on financial instruments at fair value and foreign exchange		0	0	0	0
Revenues of consolidated VIEs		0	0	0	0
Inter-segment revenues	[2]	(20)	(20)	(65)	(70)
Total revenues		(21)	(20)	(66)	(71)
Losses and loss adjustment		0	0	0	0
Amortization of deferred acquisition costs and operating		2	0	1	0
Interest		0	0	0	0
Expenses of consolidated VIEs		0	0	0	0
Inter-segment expenses	[2]	(23)	(21)	(66)	(70)
Total expenses		(21)	(21)	(65)	(70)
Income (loss) from continuing operations before income taxes		0	$ 1	(1)	(1)
Identifiable assets per segment	[3]	(1,005)		(1,005)
Net gains (losses) on extinguishment of debt				0	$ (1)
Assets held for sale		0		0
Total identifiable assets		$ (1,005)		$ (1,005)

[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.