Business Segments (Summary Of Company's Segment Results) (Detail) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021
Segment Reporting Information [Line Items]
Revenues	[1]	$ 3	$ 29	$ 30	$ 63
Net gains (losses) on financial instruments at fair value and foreign exchange		9	(20)	26	32
Net gains (losses) on extinguishment of debt		4	14	4	14
Revenues of consolidated VIEs		24	(5)	20	(19)
Inter-segment revenues	[2]	0	0	0	0
Total revenues		40	18	80	90
Losses and loss adjustment		20	9	69	107
Amortization of deferred acquisition costs and operating		12	24	33	52
Interest		43	41	84	82
Expenses of consolidated VIEs		1	5	3	16
Inter-segment expenses	[2]	0	0	0	0
Total expenses		76	79	189	257
Income (loss) before income taxes		(36)	(61)	(109)	(167)
Identifiable assets		4,067		4,067		$ 4,696
Operating Segments [Member] | US Public Finance Insurance [Member]
Segment Reporting Information [Line Items]
Revenues	[1]	(13)	21	7	44
Net gains (losses) on financial instruments at fair value and foreign exchange		(21)	3	(37)	0
Net gains (losses) on extinguishment of debt		0	0	0	0
Revenues of consolidated VIEs		0	0	0	0
Inter-segment revenues	[2]	6	6	14	14
Total revenues		(28)	30	(16)	58
Losses and loss adjustment		49	(42)	136	67
Amortization of deferred acquisition costs and operating		1	4	4	8
Interest		0	0	0	0
Expenses of consolidated VIEs		0	0	0	0
Inter-segment expenses	[2]	10	11	23	25
Total expenses		60	(27)	163	100
Income (loss) before income taxes		(88)	57	(179)	(42)
Identifiable assets		3,079		3,079
Operating Segments [Member] | Corporate Operations [Member]
Segment Reporting Information [Line Items]
Revenues	[1]	4	2	6	6
Net gains (losses) on financial instruments at fair value and foreign exchange		37	(18)	76	38
Net gains (losses) on extinguishment of debt		4	14	4	14
Revenues of consolidated VIEs		0	0	0	0
Inter-segment revenues	[2]	14	18	31	36
Total revenues		59	16	117	94
Losses and loss adjustment		0	0	0	0
Amortization of deferred acquisition costs and operating		8	17	23	38
Interest		14	14	28	28
Expenses of consolidated VIEs		0	0	0	0
Inter-segment expenses	[2]	6	4	12	10
Total expenses		28	35	63	76
Income (loss) before income taxes		31	(19)	54	18
Identifiable assets		665		665
Operating Segments [Member] | International And Structured Finance Insurance [Member]
Segment Reporting Information [Line Items]
Revenues	[1]	12	6	17	13
Net gains (losses) on financial instruments at fair value and foreign exchange		(7)	(5)	(13)	(6)
Net gains (losses) on extinguishment of debt		0	0	0	0
Revenues of consolidated VIEs		24	(5)	20	(19)
Inter-segment revenues	[2]	2	4	5	8
Total revenues		31	0	29	(4)
Losses and loss adjustment		(29)	51	(67)	40
Amortization of deferred acquisition costs and operating		3	3	6	6
Interest		29	27	56	54
Expenses of consolidated VIEs		1	5	3	16
Inter-segment expenses	[2]	5	11	14	21
Total expenses		9	97	12	137
Income (loss) before income taxes		22	(97)	17	(141)
Identifiable assets		1,729		1,729
Intersegment Elimination [Member]
Segment Reporting Information [Line Items]
Revenues	[1]	0	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)	(28)	(50)	(58)
Total revenues		(22)	(28)	(50)	(58)
Losses and loss adjustment		0	0	0	0
Amortization of deferred acquisition costs and operating		0	0	0	0
Interest		0	0	0	0
Expenses of consolidated VIEs		0	0	0	0
Inter-segment expenses	[2]	(21)	(26)	(49)	(56)
Total expenses		(21)	(26)	(49)	(56)
Income (loss) before income taxes		(1)	$ (2)	(1)	$ (2)
Identifiable assets	[3]	$ (1,406)		$ (1,406)

[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.