Business Segments (Summary Of Company's Segment Results) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014		Mar. 31, 2013		Dec. 31, 2013
Segment Reporting Information [Line Items]
Revenues	$ 142	[1]	$ 164	[1]
Net change in fair value of insured derivatives	469		(61)
Net gains (losses) on financial instruments at fair value and foreign exchange	(55)		63
Net investment losses related to other-than-temporary impairments	0		0
Net gains (losses) on extinguishment of debt	1		4
Other net realized gains (losses)	1		0
Revenues of consolidated VIEs	19		49
Inter-segment revenues	0	[2]	0	[2]
Total revenues	577		219
Losses and loss adjustment	50		(194)
Operating	56		122
Interest	54		60
Expenses of consolidated VIEs	13		16
Inter-segment expenses	0	[2]	0	[2]
Total expenses	173		4
Income (loss) before income taxes	404		215
Identifiable assets	16,087		21,592		16,953
Reportable Subsegments [Member] | Asset Liability Products Business [Member]
Segment Reporting Information [Line Items]
Revenues	9	[3]	9	[3]
Net gains (losses) on financial instruments at fair value and foreign exchange	(38)		3
Net investment losses related to other-than-temporary impairments	0		0
Net gains (losses) on extinguishment of debt	1		4
Other net realized gains (losses)	0		0
Revenues of consolidated VIEs	0		0
Inter-segment revenues	(2)	[4]	(2)	[4]
Total revenues	(30)		14
Operating	0		0
Interest	18		20
Expenses of consolidated VIEs	0		0
Inter-segment expenses	2	[4]	2	[4]
Total expenses	20		22
Income (loss) before income taxes	(50)		(8)
Identifiable assets	1,471		1,822
Reportable Subsegments [Member] | Conduits [Member]
Segment Reporting Information [Line Items]
Revenues	0	[3]	0	[3]
Net gains (losses) on financial instruments at fair value and foreign exchange	0		0
Net investment losses related to other-than-temporary impairments	0		0
Net gains (losses) on extinguishment of debt	0		0
Other net realized gains (losses)	0		0
Revenues of consolidated VIEs	4		2
Inter-segment revenues	(1)	[4]	0	[4]
Total revenues	3		2
Operating	0		0
Interest	0		0
Expenses of consolidated VIEs	0		2
Inter-segment expenses	0	[4]	11	[4]
Total expenses	0		13
Income (loss) before income taxes	3		(11)
Identifiable assets	75		692
Intersubsegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues	0	[3]	0	[3]
Net gains (losses) on financial instruments at fair value and foreign exchange	0		0
Net investment losses related to other-than-temporary impairments	0		0
Net gains (losses) on extinguishment of debt	0		0
Other net realized gains (losses)	0		0
Revenues of consolidated VIEs	0		0
Inter-segment revenues	0	[4]	0	[4]
Total revenues	0		0
Operating	0		0
Interest	0		0
Expenses of consolidated VIEs	0		0
Inter-segment expenses	0	[4]	0	[4]
Total expenses	0		0
Income (loss) before income taxes	0		0
Identifiable assets	2		(30)
U S Public Finance Insurance [Member]
Segment Reporting Information [Line Items]
Losses and loss adjustment	(14)
Operating Segments [Member] | U S Public Finance Insurance [Member]
Segment Reporting Information [Line Items]
Revenues	88	[1]	108	[1]
Net change in fair value of insured derivatives	1		0
Net gains (losses) on financial instruments at fair value and foreign exchange	4		32
Net investment losses related to other-than-temporary impairments	0		0
Net gains (losses) on extinguishment of debt	0		0
Other net realized gains (losses)	0		0
Revenues of consolidated VIEs	0		0
Inter-segment revenues	12	[2]	46	[2]
Total revenues	105		186
Losses and loss adjustment	(14)		4
Operating	9		14
Interest	0		0
Expenses of consolidated VIEs	0		0
Inter-segment expenses	18	[2]	26	[2]
Total expenses	13		44
Income (loss) before income taxes	92		142
Identifiable assets	6,124		6,874
Operating Segments [Member] | Structured Finance And International Insurance [Member]
Segment Reporting Information [Line Items]
Revenues	34	[1]	42	[1]
Net change in fair value of insured derivatives	468		(61)
Net gains (losses) on financial instruments at fair value and foreign exchange	(3)		22
Net investment losses related to other-than-temporary impairments	0		0
Net gains (losses) on extinguishment of debt	0		0
Other net realized gains (losses)	0		0
Revenues of consolidated VIEs	20		47
Inter-segment revenues	12	[2]	20	[2]
Total revenues	531		70
Losses and loss adjustment	64		(198)
Operating	16		34
Interest	27		28
Expenses of consolidated VIEs	13		14
Inter-segment expenses	19	[2]	56	[2]
Total expenses	139		(66)
Income (loss) before income taxes	392		136
Identifiable assets	10,875		17,149
Operating Segments [Member] | Advisory Services [Member]
Segment Reporting Information [Line Items]
Revenues	3	[1]	4	[1]
Net change in fair value of insured derivatives	0		0
Net gains (losses) on financial instruments at fair value and foreign exchange	(4)		0
Net investment losses related to other-than-temporary impairments	0		0
Net gains (losses) on extinguishment of debt	0		0
Other net realized gains (losses)	0		0
Revenues of consolidated VIEs	0		0
Inter-segment revenues	6	[2]	7	[2]
Total revenues	5		11
Losses and loss adjustment	0		0
Operating	11		10
Interest	0		0
Expenses of consolidated VIEs	0		0
Inter-segment expenses	1	[2]	2	[2]
Total expenses	12		12
Income (loss) before income taxes	(7)		(1)
Identifiable assets	34		34
Operating Segments [Member] | Corporate Operations [Member]
Segment Reporting Information [Line Items]
Revenues	8	[1]	1	[1]
Net change in fair value of insured derivatives	0		0
Net gains (losses) on financial instruments at fair value and foreign exchange	(14)		6
Net investment losses related to other-than-temporary impairments	0		0
Net gains (losses) on extinguishment of debt	0		0
Other net realized gains (losses)	1		0
Revenues of consolidated VIEs	(5)		0
Inter-segment revenues	16	[2]	26	[2]
Total revenues	6		33
Losses and loss adjustment	0		0
Operating	20		64
Interest	9		12
Expenses of consolidated VIEs	0		0
Inter-segment expenses	5	[2]	3	[2]
Total expenses	34		79
Income (loss) before income taxes	(28)		(46)
Identifiable assets	1,233		861
Operating Segments [Member] | Wind Down Operations [Member]
Segment Reporting Information [Line Items]
Revenues	9	[1],[3]	9	[1],[3]
Net change in fair value of insured derivatives	0		0
Net gains (losses) on financial instruments at fair value and foreign exchange	(38)		3
Net investment losses related to other-than-temporary impairments	0		0
Net gains (losses) on extinguishment of debt	1		4
Other net realized gains (losses)	0		0
Revenues of consolidated VIEs	4		2
Inter-segment revenues	(3)	[2],[4]	(2)	[2],[4]
Total revenues	(27)		16
Losses and loss adjustment	0		0
Operating	0		0
Interest	18		20
Expenses of consolidated VIEs	0		2
Inter-segment expenses	2	[2],[4]	13	[2],[4]
Total expenses	20		35
Income (loss) before income taxes	(47)		(19)
Identifiable assets	1,548		2,484
Intersegment Elimination [Member]
Segment Reporting Information [Line Items]
Revenues	0	[1]	0	[1]
Net change in fair value of insured derivatives	0		0
Net gains (losses) on financial instruments at fair value and foreign exchange	0		0
Net investment losses related to other-than-temporary impairments	0		0
Net gains (losses) on extinguishment of debt	0		0
Other net realized gains (losses)	0		0
Revenues of consolidated VIEs	0		0
Inter-segment revenues	(43)	[2]	(97)	[2]
Total revenues	(43)		(97)
Losses and loss adjustment	0		0
Operating	0		0
Interest	0		0
Expenses of consolidated VIEs	0		0
Inter-segment expenses	(45)	[2]	(100)	[2]
Total expenses	(45)		(100)
Income (loss) before income taxes	2		3
Identifiable assets	$ (3,727)	[5]	$ (5,810)	[6]

[1] Represents the sum of third-party financial guarantee net premiums earned, net investment income, insurance-related fees and reimbursements, investment management fees and other fees.

[2] Represents intercompany premium income and expense, intercompany asset management fees and expenses, and intercompany interest income and expense pertaining to intercompany receivables and payables.

[3] Represents the sum of third-party interest income, investment management services fees and other fees.

[4] Represents intercompany asset management fees and expenses plus intercompany interest income and expense pertaining to intercompany debt.

[5] Consists of intercompany reinsurance balances, repurchase agreements and deferred income taxes.

[6] Consists of intercompany reinsurance balances, repurchase agreements and loans.