Fair Value Measurement - Fair Value Level 3 Rollforward Recurring Basis (Details) - USD ($) $ in Millions		3 Months Ended				9 Months Ended
		Sep. 30, 2015		Sep. 30, 2014		Sep. 30, 2015		Sep. 30, 2014
FG VIEs' liabilities with recourse, at fair value [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value at beginning of period		$ (1,361)		$ (1,366)		$ (1,277)		$ (1,790)
Radian Asset Acquisition						(114)
Net income (loss)	[1],[2]	6		7		94		(90)
Other comprehensive income (loss)	[2]	0		0		0		0
Purchases		0		0		0		0
Settlements		40		33		113		332
FG VIE consolidations		0		0		(131)		(25)
FG VIE deconsolidations		0		0		0		247
Fair value at end of period		(1,315)		(1,326)		(1,315)		(1,326)
Change in unrealized gains/(losses) related to financial instruments held		7		6		(5)		(46)
FG VIEs' liabilities without recourse, at fair value [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value at beginning of period		(171)		(124)		(142)		(1,081)
Radian Asset Acquisition						(4)
Net income (loss)	[1],[2]	0		(13)		(30)		(49)
Other comprehensive income (loss)	[2]	0		0		0		0
Purchases		0		0		0		0
Settlements		4		4		9		16
FG VIE consolidations		0		0		0		(21)
FG VIE deconsolidations		0		0		0		1,002
Fair value at end of period		(167)		(133)		(167)		(133)
Change in unrealized gains/(losses) related to financial instruments held		(1)		(5)		(19)		(10)
Credit Risk Contract [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Fair value at beginning of period	[3]	(926)		(1,837)		(895)		(1,693)
Radian Asset Acquisition	[3]					(215)
Net income (loss)	[2],[3],[4]	86		255		300		147
Other comprehensive income (loss)	[2],[3]	0		0		0		0
Purchases	[3]	0		0		0		0
Settlements	[3]	(7)		14		(37)		(22)
FG VIE consolidations	[3]	0		0		0		0
FG VIE deconsolidations	[3]	0		0		0		0
Fair value at end of period	[3]	(847)		(1,568)		(847)		(1,568)
Change in unrealized gains/(losses) related to financial instruments held	[3]	(19)		98		166		(47)
Obligations of state and political subdivisions [Member]
Fair Value Level 3 Rollforward
Fair value at beginning of period		655		748		770		730
Radian Asset Acquisition						4
Net Income (loss)	[2],[5]	(3)		(4)		17		14
Other comprehensive income (loss)	[2]	(10)		25		(9)		27
Purchases		250		159		260		212
Settlements		(9)		(15)		(158)	[6]	(83)
FG VIE Consolidations		0		0		(1)		0
FG VIE deconsolidations		0		0		0		13
Fair value at end of period		883		913		883		913
Change in unrealized gains/(losses) related to financial instruments held		(10)		25		(4)		25
Short-term Investments [Member]
Fair Value Level 3 Rollforward
Fair value at beginning of period		0				0
Radian Asset Acquisition						0
Net Income (loss)	[2],[5]	8				8
Other comprehensive income (loss)	[2]	(4)				(4)
Purchases	[6]	52				52
Settlements		(6)				(6)
FG VIE Consolidations		0				0
FG VIE deconsolidations		0				0
Fair value at end of period		50				50
Change in unrealized gains/(losses) related to financial instruments held		(4)				(4)
Other invested assets [Member]
Fair Value Level 3 Rollforward
Fair value at beginning of period		78		49		78		2
Radian Asset Acquisition						2
Net Income (loss)	[2]	4	[5]	0	[5]	8	[5]	0
Other comprehensive income (loss)	[2]	(4)		2		(6)		4
Purchases		0		25		0		70	[6]
Settlements		(30)		0		(34)		0
FG VIE Consolidations		0		0		0		0
FG VIE deconsolidations		0		0		0		0
Fair value at end of period		48		76		48		76
Change in unrealized gains/(losses) related to financial instruments held		0		2		(2)		4
FG VIEs' assets, at fair value [Member]
Fair Value Level 3 Rollforward
Fair value at beginning of period		1,596		1,284		1,398		2,565
Radian Asset Acquisition						122
Net Income (loss)	[1],[2]	(11)		43		31		160
Other comprehensive income (loss)	[2]	0		0		0		0
Purchases		0		0		0		0
Settlements		(44)		(31)		(114)		(346)
FG VIE Consolidations		0		0		104		46
FG VIE deconsolidations		0		0		0		(1,129)
Fair value at end of period		1,541		1,296		1,541		1,296
Change in unrealized gains/(losses) related to financial instruments held		3		55		68		120
Other assets [Member]
Fair Value Level 3 Rollforward
Fair value at beginning of period		60		31		35		46
Radian Asset Acquisition						0
Net Income (loss)	[2],[7]	(15)		4		10		(11)
Other comprehensive income (loss)	[2]	0		0		0		0
Purchases		0		0		0		0
Settlements		0		0		0		0
FG VIE Consolidations		0		0		0		0
FG VIE deconsolidations		0		0		0		0
Fair value at end of period		45		35		45		35
Change in unrealized gains/(losses) related to financial instruments held		$ (15)		$ 4		$ 10		$ (11)

[1] Included in fair value gains (losses) on FG VIEs.

[2] Realized and unrealized gains (losses) from changes in values of Level 3 financial instruments represent gains (losses) from changes in values of those financial instruments only for the periods in which the instruments were classified as Level 3.

[3] Represents net position of credit derivatives. The consolidated balance sheet presents gross assets and liabilities based on net counterparty exposure.

[4] Reported in net change in fair value of credit derivatives.

[5] Included in net realized investment gains (losses) and net investment income.

[6] Includes a non-cash transaction.

[7] Recorded in fair value gains (losses) on CCS.