Expected Loss to be Paid - Net Expected Loss to be Paid After Net Expected Recoveries for Breaches of R&W Rollforward (Details) - USD ($) $ in Millions		3 Months Ended			9 Months Ended
		Sep. 30, 2015		Sep. 30, 2014	Sep. 30, 2015		Sep. 30, 2014		Dec. 31, 2014
Present Value of Net Expected Loss and Loss Adjustment Expenses to be Paid [Roll Forward]
Beginning of Period, Net Expected Loss to be Paid After Recoveries for R&W		$ 1,510		$ 1,035	$ 1,169	[1]	$ 982
Net expected loss to be paid on Radian Asset portfolio as of April 1, 2015					190
Economic loss development after recoveries for R&W		(3)		(63)	186		(28)
Accretion of discount		10			24
Changes in discount rates		11			(29)
Changes in timing and assumptions		(24)			191
(Paid) Recovered Losses After Recoveries for R&W	[2]	(200)		(39)	(238)		(21)
End of Period, Net Expected Loss to be Paid After Recoveries for R&W		1,307	[1]	933	$ 1,307	[1]	933
Period after the end of the reporting period within which the ceded paid losses are typically settled (in days)					45 days
Loss and LAE Reserve paid		7		6	$ 16		20
Expected LAE to be paid		13			13				$ 16
Subtotal [Member]
Present Value of Net Expected Loss and Loss Adjustment Expenses to be Paid [Roll Forward]
Beginning of Period, Net Expected Loss to be Paid After Recoveries for R&W					1,169
Economic loss development after recoveries for R&W		(3)		(63)	186		(28)
End of Period, Net Expected Loss to be Paid After Recoveries for R&W		1,307			1,307
Public Finance [Member]
Present Value of Net Expected Loss and Loss Adjustment Expenses to be Paid [Roll Forward]
Beginning of Period, Net Expected Loss to be Paid After Recoveries for R&W		657		391	348	[1]	321
Net expected loss to be paid on Radian Asset portfolio as of April 1, 2015					85
Economic loss development after recoveries for R&W		91		1	321		101
(Paid) Recovered Losses After Recoveries for R&W	[2]	(18)		(8)	(24)		(38)
End of Period, Net Expected Loss to be Paid After Recoveries for R&W		730	[1]	384	730	[1]	384
Public Finance [Member] | United States [Member]
Present Value of Net Expected Loss and Loss Adjustment Expenses to be Paid [Roll Forward]
Beginning of Period, Net Expected Loss to be Paid After Recoveries for R&W		613		339	303	[1]	264
Net expected loss to be paid on Radian Asset portfolio as of April 1, 2015					81
Economic loss development after recoveries for R&W		92		2	327		107
(Paid) Recovered Losses After Recoveries for R&W	[2]	(18)		(8)	(24)		(38)
End of Period, Net Expected Loss to be Paid After Recoveries for R&W		687	[1]	333	687	[1]	333
Public Finance [Member] | Non United States [Member]
Present Value of Net Expected Loss and Loss Adjustment Expenses to be Paid [Roll Forward]
Beginning of Period, Net Expected Loss to be Paid After Recoveries for R&W		44		52	45	[1]	57
Net expected loss to be paid on Radian Asset portfolio as of April 1, 2015					4
Economic loss development after recoveries for R&W		(1)		(1)	(6)		(6)
(Paid) Recovered Losses After Recoveries for R&W	[2]	0		0	0		0
End of Period, Net Expected Loss to be Paid After Recoveries for R&W		43	[1]	51	43	[1]	51
RMBS [Member] | United States [Member]
Present Value of Net Expected Loss and Loss Adjustment Expenses to be Paid [Roll Forward]
Beginning of Period, Net Expected Loss to be Paid After Recoveries for R&W		524		476	584	[1]	493
Net expected loss to be paid on Radian Asset portfolio as of April 1, 2015					4
Economic loss development after recoveries for R&W		(76)		(62)	(104)		(131)
(Paid) Recovered Losses After Recoveries for R&W	[2]	(113)		(33)	(149)		19
End of Period, Net Expected Loss to be Paid After Recoveries for R&W		335	[1]	381	335	[1]	381
RMBS [Member] | First Lien [Member] | United States [Member]
Present Value of Net Expected Loss and Loss Adjustment Expenses to be Paid [Roll Forward]
Beginning of Period, Net Expected Loss to be Paid After Recoveries for R&W		521		602	595	[1]	620
Net expected loss to be paid on Radian Asset portfolio as of April 1, 2015					3
Economic loss development after recoveries for R&W		(89)		(30)	(117)		(68)
(Paid) Recovered Losses After Recoveries for R&W	[2]	(123)		(38)	(172)		(18)
End of Period, Net Expected Loss to be Paid After Recoveries for R&W		309	[1]	534	309	[1]	534
RMBS [Member] | First Lien [Member] | Prime [Member] | United States [Member]
Present Value of Net Expected Loss and Loss Adjustment Expenses to be Paid [Roll Forward]
Beginning of Period, Net Expected Loss to be Paid After Recoveries for R&W		1		11	4	[1]	21
Net expected loss to be paid on Radian Asset portfolio as of April 1, 2015					0
Economic loss development after recoveries for R&W		0		(1)	(1)		(11)
(Paid) Recovered Losses After Recoveries for R&W	[2]	(1)		0	(3)		0
End of Period, Net Expected Loss to be Paid After Recoveries for R&W		0	[1]	10	0	[1]	10
RMBS [Member] | First Lien [Member] | Alt-A [Member] | United States [Member]
Present Value of Net Expected Loss and Loss Adjustment Expenses to be Paid [Roll Forward]
Beginning of Period, Net Expected Loss to be Paid After Recoveries for R&W		265		301	304	[1]	304
Net expected loss to be paid on Radian Asset portfolio as of April 1, 2015					7
Economic loss development after recoveries for R&W		(111)		(18)	(132)		(6)
(Paid) Recovered Losses After Recoveries for R&W	[2]	(108)		(35)	(133)		(50)
End of Period, Net Expected Loss to be Paid After Recoveries for R&W		46	[1]	248	46	[1]	248
RMBS [Member] | First Lien [Member] | Option ARM [Member] | United States [Member]
Present Value of Net Expected Loss and Loss Adjustment Expenses to be Paid [Roll Forward]
Beginning of Period, Net Expected Loss to be Paid After Recoveries for R&W		(18)		(51)	(16)	[1]	(9)
Net expected loss to be paid on Radian Asset portfolio as of April 1, 2015					0
Economic loss development after recoveries for R&W		(4)		0	(3)		(39)
(Paid) Recovered Losses After Recoveries for R&W	[2]	6		20	3		17
End of Period, Net Expected Loss to be Paid After Recoveries for R&W		(16)	[1]	(31)	(16)	[1]	(31)
RMBS [Member] | First Lien [Member] | Subprime [Member] | United States [Member]
Present Value of Net Expected Loss and Loss Adjustment Expenses to be Paid [Roll Forward]
Beginning of Period, Net Expected Loss to be Paid After Recoveries for R&W		273		341	303	[1]	304
Net expected loss to be paid on Radian Asset portfolio as of April 1, 2015					(4)
Economic loss development after recoveries for R&W		26		(11)	19		(12)
(Paid) Recovered Losses After Recoveries for R&W	[2]	(20)		(23)	(39)		15
End of Period, Net Expected Loss to be Paid After Recoveries for R&W		279	[1]	307	279	[1]	307
RMBS [Member] | Second Lien [Member] | United States [Member]
Present Value of Net Expected Loss and Loss Adjustment Expenses to be Paid [Roll Forward]
Beginning of Period, Net Expected Loss to be Paid After Recoveries for R&W		3		(126)	(11)	[1]	(127)
Net expected loss to be paid on Radian Asset portfolio as of April 1, 2015					1
Economic loss development after recoveries for R&W		13		(32)	13		(63)
(Paid) Recovered Losses After Recoveries for R&W	[2]	10		5	23		37
End of Period, Net Expected Loss to be Paid After Recoveries for R&W		26	[1]	(153)	26	[1]	(153)
RMBS [Member] | Second Lien [Member] | Closed-end [Member] | United States [Member]
Present Value of Net Expected Loss and Loss Adjustment Expenses to be Paid [Roll Forward]
Beginning of Period, Net Expected Loss to be Paid After Recoveries for R&W		9		(9)	8	[1]	(11)
Net expected loss to be paid on Radian Asset portfolio as of April 1, 2015					0
Economic loss development after recoveries for R&W		0		2	(2)		2
(Paid) Recovered Losses After Recoveries for R&W	[2]	2		2	5		4
End of Period, Net Expected Loss to be Paid After Recoveries for R&W		11	[1]	(5)	11	[1]	(5)
RMBS [Member] | Second Lien [Member] | HELOCs [Member] | United States [Member]
Present Value of Net Expected Loss and Loss Adjustment Expenses to be Paid [Roll Forward]
Beginning of Period, Net Expected Loss to be Paid After Recoveries for R&W		(6)		(117)	(19)	[1]	(116)
Net expected loss to be paid on Radian Asset portfolio as of April 1, 2015					1
Economic loss development after recoveries for R&W		13		(34)	15		(65)
(Paid) Recovered Losses After Recoveries for R&W	[2]	8		3	18		33
End of Period, Net Expected Loss to be Paid After Recoveries for R&W		15	[1]	(148)	15	[1]	(148)
Triple-X Life Insurance Transaction [Member]
Present Value of Net Expected Loss and Loss Adjustment Expenses to be Paid [Roll Forward]
Beginning of Period, Net Expected Loss to be Paid After Recoveries for R&W		165		90	161	[1]	75
Net expected loss to be paid on Radian Asset portfolio as of April 1, 2015					0
Economic loss development after recoveries for R&W		1		3	8		21
(Paid) Recovered Losses After Recoveries for R&W	[2]	(68)		(1)	(71)		(4)
End of Period, Net Expected Loss to be Paid After Recoveries for R&W		98	[1]	92	98	[1]	92
Trust Preferred Securities (TruPS) [Member]
Present Value of Net Expected Loss and Loss Adjustment Expenses to be Paid [Roll Forward]
Beginning of Period, Net Expected Loss to be Paid After Recoveries for R&W		10		32	23	[1]	51
Net expected loss to be paid on Radian Asset portfolio as of April 1, 2015					0
Economic loss development after recoveries for R&W		(5)		(5)	(18)		(24)	[3]
(Paid) Recovered Losses After Recoveries for R&W	[2]	0		(1)	0		(1)
End of Period, Net Expected Loss to be Paid After Recoveries for R&W		5	[1]	26	5	[1]	26
Student Loan [Member]
Present Value of Net Expected Loss and Loss Adjustment Expenses to be Paid [Roll Forward]
Beginning of Period, Net Expected Loss to be Paid After Recoveries for R&W		58		58	68	[1]	52
Net expected loss to be paid on Radian Asset portfolio as of April 1, 2015					0
Economic loss development after recoveries for R&W		(2)		6	(7)		12	[3]
(Paid) Recovered Losses After Recoveries for R&W	[2]	0		0	(5)		0
End of Period, Net Expected Loss to be Paid After Recoveries for R&W		56	[1]	64	56	[1]	64
Other structured finance [Member]
Present Value of Net Expected Loss and Loss Adjustment Expenses to be Paid [Roll Forward]
Beginning of Period, Net Expected Loss to be Paid After Recoveries for R&W		96		(12)	(15)	[1]	(10)
Net expected loss to be paid on Radian Asset portfolio as of April 1, 2015					101
Economic loss development after recoveries for R&W		(12)		(6)	(14)		(7)
(Paid) Recovered Losses After Recoveries for R&W	[2]	(1)		4	11		3
End of Period, Net Expected Loss to be Paid After Recoveries for R&W		83	[1]	(14)	83	[1]	(14)
Structured Finance [Member]
Present Value of Net Expected Loss and Loss Adjustment Expenses to be Paid [Roll Forward]
Beginning of Period, Net Expected Loss to be Paid After Recoveries for R&W		853		644	821	[1]	661
Net expected loss to be paid on Radian Asset portfolio as of April 1, 2015					105
Economic loss development after recoveries for R&W		(94)		(64)	(135)		(129)
(Paid) Recovered Losses After Recoveries for R&W	[2]	(182)		(31)	(214)		17
End of Period, Net Expected Loss to be Paid After Recoveries for R&W		577	[1]	$ 549	577	[1]	$ 549
Radian [Member]
Present Value of Net Expected Loss and Loss Adjustment Expenses to be Paid [Roll Forward]
Net expected loss to be paid on Radian Asset portfolio as of April 1, 2015		$ 0			$ 190

[1] Includes expected LAE to be paid of $13 million as of September 30, 2015 and $16 million as of December 31, 2014.

[2] Net of ceded paid losses, whether or not such amounts have been settled with reinsurers. Ceded paid losses are typically settled 45 days after the end of the reporting period. Such amounts are recorded in reinsurance recoverable on paid losses included in other assets. The Company paid $7 million and $6 million in LAE for Third Quarter 2015 and 2014, respectively, and $16 million and $20 million in LAE for Nine Months 2015 and 2014, respectively.

[3] Refer to Note 9, Financial Guaranty Contracts Accounted for as Credit Derivatives.