Business Segments (Summary Of Company's Segment Results) (Detail) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022	Dec. 31, 2022
Segment Reporting Information [Line Items]
Revenues	[1]	$ 40	$ 3	$ 72	$ 30
Net gains (losses) on financial instruments at fair value and foreign exchange		11	9	(1)	26
Net gains (losses) on extinguishment of debt		1	4	1	4
Revenues of consolidated VIEs		(24)	24	(42)	20
Inter-segment revenues	[2]	0	0	0	0
Total revenues		28	40	30	80
Losses and loss adjustment		28	20	35	69
Amortization of deferred acquisition costs and operating		21	12	44	33
Interest		53	43	104	84
Expenses of consolidated VIEs		4	1	8	3
Inter-segment expenses	[2]	0	0	0	0
Total expenses		106	76	191	189
Income (loss) from continuing operations before income taxes		(78)	(36)	(161)	(109)
Identifiable assets per segment		3,169		3,169
Assets held for sale		88		88
Total identifiable assets		3,257		3,257		$ 3,375
Operating Segments [Member] | US Public Finance Insurance [Member]
Segment Reporting Information [Line Items]
Revenues	[1]	19	(13)	41	7
Net gains (losses) on financial instruments at fair value and foreign exchange		0	(21)	2	(37)
Net gains (losses) on extinguishment of debt		0	0	0	0
Revenues of consolidated VIEs		0	0	0	0
Inter-segment revenues	[2]	7	6	14	14
Total revenues		26	(28)	57	(16)
Losses and loss adjustment		26	49	26	136
Amortization of deferred acquisition costs and operating		2	1	4	4
Interest		0	0	0	0
Expenses of consolidated VIEs		0	0	0	0
Inter-segment expenses	[2]	9	10	21	23
Total expenses		37	60	51	163
Income (loss) from continuing operations before income taxes		(11)	(88)	6	(179)
Identifiable assets per segment		2,453		2,453
Assets held for sale		0		0
Total identifiable assets		2,453		2,453
Operating Segments [Member] | Corporate Operations [Member]
Segment Reporting Information [Line Items]
Revenues	[1]	3	4	7	6
Net gains (losses) on financial instruments at fair value and foreign exchange		13	37	2	76
Net gains (losses) on extinguishment of debt		1	4	1	4
Revenues of consolidated VIEs		0	0	0	0
Inter-segment revenues	[2]	14	14	28	31
Total revenues		31	59	38	117
Losses and loss adjustment		0	0	0	0
Amortization of deferred acquisition costs and operating		18	8	36	23
Interest		14	14	28	28
Expenses of consolidated VIEs		0	0	0	0
Inter-segment expenses	[2]	5	6	11	12
Total expenses		37	28	75	63
Income (loss) from continuing operations before income taxes		(6)	31	(37)	54
Identifiable assets per segment		611		611
Assets held for sale		0		0
Total identifiable assets		611		611
Operating Segments [Member] | International And Structured Finance Insurance [Member]
Segment Reporting Information [Line Items]
Revenues	[1]	17	12	24	17
Net gains (losses) on financial instruments at fair value and foreign exchange		(2)	(7)	(5)	(13)
Net gains (losses) on extinguishment of debt		0	0	0	0
Revenues of consolidated VIEs		(24)	24	(42)	20
Inter-segment revenues	[2]	1	2	3	5
Total revenues		(8)	31	(20)	29
Losses and loss adjustment		2	(29)	9	(67)
Amortization of deferred acquisition costs and operating		2	3	5	6
Interest		40	29	76	56
Expenses of consolidated VIEs		4	1	8	3
Inter-segment expenses	[2]	5	5	12	14
Total expenses		53	9	110	12
Income (loss) from continuing operations before income taxes		(61)	22	(130)	17
Identifiable assets per segment		1,038		1,038
Assets held for sale		0		0
Total identifiable assets		1,038		1,038
Intersegment Elimination [Member]
Segment Reporting Information [Line Items]
Revenues	[1]	1	0	0	0
Net gains (losses) on financial instruments at fair value and foreign exchange		0	0	0	0
Net gains (losses) on extinguishment of debt		0	0	0	0
Revenues of consolidated VIEs		0	0	0	0
Inter-segment revenues	[2]	(22)	(22)	(45)	(50)
Total revenues		(21)	(22)	(45)	(50)
Losses and loss adjustment		0	0	0	0
Amortization of deferred acquisition costs and operating		(1)	0	(1)	0
Interest		(1)	0	0	0
Expenses of consolidated VIEs		0	0	0	0
Inter-segment expenses	[2]	(19)	(21)	(44)	(49)
Total expenses		(21)	(21)	(45)	(49)
Income (loss) from continuing operations before income taxes		0	$ (1)	0	$ (1)
Identifiable assets per segment	[3]	(933)		(933)
Assets held for sale		0		0
Total identifiable assets		$ (933)		$ (933)

[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.