Business Segments (Summary Of Company's Segment Results) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2014		Jun. 30, 2013		Jun. 30, 2014		Jun. 30, 2013		Dec. 31, 2013
Segment Reporting Information [Line Items]
Revenues	$ 135	[1]	$ 168	[1]	$ 277	[1]	$ 332	[1]
Net change in fair value of insured derivatives	(47)		(182)		422		(243)
Net gains (losses) on financial instruments at fair value and foreign exchange	61		(6)		6		57
Net investment losses related to other-than-temporary impairments	0		0		0		0
Net gains (losses) on extinguishment of debt	2		39		3		43
Other net realized gains (losses)	0		0		1		0
Revenues of consolidated VIEs	36		93		55		142
Inter-segment revenues	0	[2]	0	[2]	0	[3]	0	[3]
Total revenues	187		112		764		331
Losses and loss adjustment	12		188		62		(6)
Operating	57		114		113		236
Interest	52		60		106		120
Expenses of consolidated VIEs	11		14		24		30
Inter-segment expenses	0	[2]	0	[2]	0	[3]	0	[3]
Total expenses	132		376		305		380
Income (loss) before income taxes	55		(264)		459		(49)
Identifiable assets	16,024		18,122		16,024		18,122		16,953
Reportable Subsegments [Member] | Asset Liability Products Business [Member]
Segment Reporting Information [Line Items]
Revenues	6	[4]	6	[4]	15	[4]	15	[4]
Net gains (losses) on financial instruments at fair value and foreign exchange	(20)		(12)		(58)		(9)
Net investment losses related to other-than-temporary impairments	0		0		0		0
Net gains (losses) on extinguishment of debt	2		0		3		4
Other net realized gains (losses)	0		0		0		0
Revenues of consolidated VIEs	0		0		0		0
Inter-segment revenues	(2)	[5]	0	[5]	(4)	[5]	(2)	[5]
Total revenues	(14)		(6)		(44)		8
Operating	1		1		1		1
Interest	14		20		32		40
Expenses of consolidated VIEs	0		0		0		0
Inter-segment expenses	2	[5]	2	[5]	4	[5]	4	[5]
Total expenses	17		23		37		45
Income (loss) before income taxes	(31)		(29)		(81)		(37)
Identifiable assets	1,498		1,638		1,498		1,638
Reportable Subsegments [Member] | Conduits [Member]
Segment Reporting Information [Line Items]
Revenues	0	[4]	0	[4]	0	[4]	0	[4]
Net gains (losses) on financial instruments at fair value and foreign exchange	0		0		0		0
Net investment losses related to other-than-temporary impairments	0		0		0		0
Net gains (losses) on extinguishment of debt	0		0		0		0
Other net realized gains (losses)	0		0		0		0
Revenues of consolidated VIEs	0		5		4		7
Inter-segment revenues	0	[5]	(7)	[5]	(1)	[5]	(7)	[5]
Total revenues	0		(2)		3		0
Operating	0		0		0		0
Interest	0		0		0		0
Expenses of consolidated VIEs	0		2		0		4
Inter-segment expenses	9	[5]	0	[5]	9	[5]	11	[5]
Total expenses	9		2		9		15
Income (loss) before income taxes	(9)		(4)		(6)		(15)
Identifiable assets	0		359		0		359
Intersubsegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues	0	[4]	0	[4]	0	[4]	0	[4]
Net gains (losses) on financial instruments at fair value and foreign exchange	0		0		0		0
Net investment losses related to other-than-temporary impairments	0		0		0		0
Net gains (losses) on extinguishment of debt	0		0		0		0
Other net realized gains (losses)	0		0		0		0
Revenues of consolidated VIEs	0		0		0		0
Inter-segment revenues	0	[5]	7	[5]	0	[5]	7	[5]
Total revenues	0		7		0		7
Operating	0		0		0		0
Interest	0		0		0		0
Expenses of consolidated VIEs	0		0		0		0
Inter-segment expenses	0	[5]	0	[5]	0	[5]	0	[5]
Total expenses	0		0		0		0
Income (loss) before income taxes	0		7		0		7
Identifiable assets	0		12		0		12
U S Public Finance Insurance [Member]
Segment Reporting Information [Line Items]
Losses and loss adjustment					3
Operating Segments [Member] | U S Public Finance Insurance [Member]
Segment Reporting Information [Line Items]
Revenues	84	[1]	113	[1]	172	[1]	221	[1]
Net change in fair value of insured derivatives	0		0		1		0
Net gains (losses) on financial instruments at fair value and foreign exchange	15		(2)		19		30
Net investment losses related to other-than-temporary impairments	0		0		0		0
Net gains (losses) on extinguishment of debt	0		22		0		22
Other net realized gains (losses)	0		0		0		0
Revenues of consolidated VIEs	0		0		0		0
Inter-segment revenues	11	[2]	3	[2]	23	[3]	49	[3]
Total revenues	110		136		215		322
Losses and loss adjustment	17		66		3		70
Operating	11		30		20		44
Interest	0		0		0		0
Expenses of consolidated VIEs	0		0		0		0
Inter-segment expenses	20	[2]	26	[2]	38	[3]	52	[3]
Total expenses	48		122		61		166
Income (loss) before income taxes	62		14		154		156
Identifiable assets	6,194		6,651		6,194		6,651
Operating Segments [Member] | Structured Finance And International Insurance [Member]
Segment Reporting Information [Line Items]
Revenues	43	[1]	39	[1]	77	[1]	81	[1]
Net change in fair value of insured derivatives	(47)		(182)		421		(243)
Net gains (losses) on financial instruments at fair value and foreign exchange	13		12		10		34
Net investment losses related to other-than-temporary impairments	0		0		0		0
Net gains (losses) on extinguishment of debt	0		17		0		17
Other net realized gains (losses)	0		0		0		0
Revenues of consolidated VIEs	31		97		51		144
Inter-segment revenues	13	[2]	(5)	[2]	25	[3]	15	[3]
Total revenues	53		(22)		584		48
Losses and loss adjustment	(5)		122		59		(76)
Operating	16		35		32		69
Interest	27		29		54		57
Expenses of consolidated VIEs	11		12		24		26
Inter-segment expenses	16	[2]	36	[2]	35	[3]	92	[3]
Total expenses	65		234		204		168
Income (loss) before income taxes	(12)		(256)		380		(120)
Identifiable assets	10,787		12,669		10,787		12,669
Operating Segments [Member] | Advisory Services [Member]
Segment Reporting Information [Line Items]
Revenues	4	[1]	6	[1]	7	[1]	10	[1]
Net change in fair value of insured derivatives	0		0		0		0
Net gains (losses) on financial instruments at fair value and foreign exchange	1		0		(3)		0
Net investment losses related to other-than-temporary impairments	0		0		0		0
Net gains (losses) on extinguishment of debt	0		0		0		0
Other net realized gains (losses)	0		0		0		0
Revenues of consolidated VIEs	0		0		0		0
Inter-segment revenues	6	[2]	5	[2]	12	[3]	12	[3]
Total revenues	11		11		16		22
Losses and loss adjustment	0		0		0		0
Operating	11		16		22		26
Interest	0		0		0		0
Expenses of consolidated VIEs	0		0		0		0
Inter-segment expenses	2	[2]	1	[2]	3	[3]	3	[3]
Total expenses	13		17		25		29
Income (loss) before income taxes	(2)		(6)		(9)		(7)
Identifiable assets	38		46		38		46
Operating Segments [Member] | Corporate Operations [Member]
Segment Reporting Information [Line Items]
Revenues	(2)	[1]	4	[1]	6	[1]	5	[1]
Net change in fair value of insured derivatives	0		0		0		0
Net gains (losses) on financial instruments at fair value and foreign exchange	52		(4)		38		2
Net investment losses related to other-than-temporary impairments	0		0		0		0
Net gains (losses) on extinguishment of debt	0		0		0		0
Other net realized gains (losses)	0		0		1		0
Revenues of consolidated VIEs	5		(9)		0		(9)
Inter-segment revenues	67	[2]	(5)	[2]	83	[3]	21	[3]
Total revenues	122		(14)		128		19
Losses and loss adjustment	0		0		0		0
Operating	18		32		38		96
Interest	11		11		20		23
Expenses of consolidated VIEs	0		0		0		0
Inter-segment expenses	5	[2]	2	[2]	10	[3]	5	[3]
Total expenses	34		45		68		124
Income (loss) before income taxes	88		(59)		60		(105)
Identifiable assets	1,173		931		1,173		931
Operating Segments [Member] | Wind Down Operations [Member]
Segment Reporting Information [Line Items]
Revenues	6	[1],[4]	6	[1],[4]	15	[1],[4]	15	[1],[4]
Net change in fair value of insured derivatives	0		0		0		0
Net gains (losses) on financial instruments at fair value and foreign exchange	(20)		(12)		(58)		(9)
Net investment losses related to other-than-temporary impairments	0		0		0		0
Net gains (losses) on extinguishment of debt	2		0		3		4
Other net realized gains (losses)	0		0		0		0
Revenues of consolidated VIEs	0		5		4		7
Inter-segment revenues	(2)	[2],[5]	0	[2],[5]	(5)	[3],[5]	(2)	[3],[5]
Total revenues	(14)		(1)		(41)		15
Losses and loss adjustment	0		0		0		0
Operating	1		1		1		1
Interest	14		20		32		40
Expenses of consolidated VIEs	0		2		0		4
Inter-segment expenses	11	[2],[5]	2	[2],[5]	13	[3],[5]	15	[3],[5]
Total expenses	26		25		46		60
Income (loss) before income taxes	(40)		(26)		(87)		(45)
Identifiable assets	1,498		2,009		1,498		2,009
Intersegment Elimination [Member]
Segment Reporting Information [Line Items]
Revenues	0	[1]	0	[1]	0	[1]	0	[1]
Net change in fair value of insured derivatives	0		0		0		0
Net gains (losses) on financial instruments at fair value and foreign exchange	0		0		0		0
Net investment losses related to other-than-temporary impairments	0		0		0		0
Net gains (losses) on extinguishment of debt	0		0		0		0
Other net realized gains (losses)	0		0		0		0
Revenues of consolidated VIEs	0		0		0		0
Inter-segment revenues	(95)	[2]	2	[2]	(138)	[3]	(95)	[3]
Total revenues	(95)		2		(138)		(95)
Losses and loss adjustment	0		0		0		0
Operating	0		0		0		0
Interest	0		0		0		0
Expenses of consolidated VIEs	0		0		0		0
Inter-segment expenses	(54)	[2]	(67)	[2]	(99)	[3]	(167)	[3]
Total expenses	(54)		(67)		(99)		(167)
Income (loss) before income taxes	(41)		69		(39)		72
Identifiable assets	$ (3,666)	[6]	$ (4,184)	[6]	$ (3,666)	[6]	$ (4,184)	[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 intercompany premium income and expense, intercompany asset management fees and expenses, intercompany interest income and expense pertaining to intercompany receivables and payables and intercompany loans.

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

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

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