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			6 Months Ended
		Jun. 30, 2015		Jun. 30, 2014	Jun. 30, 2015		Jun. 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		$ 1,154		$ 984	$ 1,169	[1]	$ 982
Economic loss development after recoveries for R&W		192		23	189		35
Accretion of discount		7			14
Changes in discount rates		(47)			(40)
Changes in timing and assumptions		232			215
(Paid) Recovered Losses After Recoveries for R&W	[2]	(26)		28	(38)		18
End of Period, Net Expected Loss to be Paid After Recoveries for R&W		1,510	[1]	1,035	$ 1,510	[1]	1,035
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		5		8	$ 9		14
Expected LAE to be paid		15			15				$ 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		192		23	189		35
End of Period, Net Expected Loss to be Paid After Recoveries for R&W		1,510			1,510
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		352		338	348	[1]	321
Economic loss development after recoveries for R&W		224		77	230		100
(Paid) Recovered Losses After Recoveries for R&W	[2]	(4)		(24)	(6)		(30)
End of Period, Net Expected Loss to be Paid After Recoveries for R&W		657	[1]	391	657	[1]	391
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		310		281	303	[1]	264
Economic loss development after recoveries for R&W		226		82	235		105
(Paid) Recovered Losses After Recoveries for R&W	[2]	(4)		(24)	(6)		(30)
End of Period, Net Expected Loss to be Paid After Recoveries for R&W		613	[1]	339	613	[1]	339
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		42		57	45	[1]	57
Economic loss development after recoveries for R&W		(2)		(5)	(5)		(5)
(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		44	[1]	52	44	[1]	52
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		570		480	584	[1]	493
Economic loss development after recoveries for R&W		(32)		(59)	(28)		(69)
(Paid) Recovered Losses After Recoveries for R&W	[2]	(18)		55	(36)		52
End of Period, Net Expected Loss to be Paid After Recoveries for R&W		524	[1]	476	524	[1]	476
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		569		593	595	[1]	620
Economic loss development after recoveries for R&W		(26)		(21)	(28)		(38)
(Paid) Recovered Losses After Recoveries for R&W	[2]	(25)		30	(49)		20
End of Period, Net Expected Loss to be Paid After Recoveries for R&W		521	[1]	602	521	[1]	602
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		3		18	4	[1]	21
Economic loss development after recoveries for R&W		(1)		(7)	(1)		(10)
(Paid) Recovered Losses After Recoveries for R&W	[2]	(1)		0	(2)		0
End of Period, Net Expected Loss to be Paid After Recoveries for R&W		1	[1]	11	1	[1]	11
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		289		308	304	[1]	304
Economic loss development after recoveries for R&W		(16)		4	(21)		12
(Paid) Recovered Losses After Recoveries for R&W	[2]	(15)		(11)	(25)		(15)
End of Period, Net Expected Loss to be Paid After Recoveries for R&W		265	[1]	301	265	[1]	301
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		(16)		(28)	(16)	[1]	(9)
Economic loss development after recoveries for R&W		(3)		(24)	1		(39)
(Paid) Recovered Losses After Recoveries for R&W	[2]	1		1	(3)		(3)
End of Period, Net Expected Loss to be Paid After Recoveries for R&W		(18)	[1]	(51)	(18)	[1]	(51)
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		293		295	303	[1]	304
Economic loss development after recoveries for R&W		(6)		6	(7)		(1)
(Paid) Recovered Losses After Recoveries for R&W	[2]	(10)		40	(19)		38
End of Period, Net Expected Loss to be Paid After Recoveries for R&W		273	[1]	341	273	[1]	341
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		1		(113)	(11)	[1]	(127)
Economic loss development after recoveries for R&W		(6)		(38)	0		(31)
(Paid) Recovered Losses After Recoveries for R&W	[2]	7		25	13		32
End of Period, Net Expected Loss to be Paid After Recoveries for R&W		3	[1]	(126)	3	[1]	(126)
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		11		(4)	8	[1]	(11)
Economic loss development after recoveries for R&W		(3)		(5)	(2)		0
(Paid) Recovered Losses After Recoveries for R&W	[2]	1		0	3		2
End of Period, Net Expected Loss to be Paid After Recoveries for R&W		9	[1]	(9)	9	[1]	(9)
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		(10)		(109)	(19)	[1]	(116)
Economic loss development after recoveries for R&W		(3)		(33)	2		(31)
(Paid) Recovered Losses After Recoveries for R&W	[2]	6		25	10		30
End of Period, Net Expected Loss to be Paid After Recoveries for R&W		(6)	[1]	(117)	(6)	[1]	(117)
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		87	161	[1]	75
Economic loss development after recoveries for R&W		2		1	7		14
(Paid) Recovered Losses After Recoveries for R&W	[2]	(2)		(1)	(3)		(2)
End of Period, Net Expected Loss to be Paid After Recoveries for R&W		165	[1]	87	165	[1]	87
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		14		32	23	[1]	51
Economic loss development after recoveries for R&W		(4)		0	(13)		(19)	[3]
(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		10	[1]	32	10	[1]	32
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		62		54	68	[1]	52
Economic loss development after recoveries for R&W		1		4	(5)		6	[3]
(Paid) Recovered Losses After Recoveries for R&W	[2]	(5)		0	(5)		0
End of Period, Net Expected Loss to be Paid After Recoveries for R&W		58	[1]	58	58	[1]	58
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		(9)		(7)	(15)	[1]	(10)
Economic loss development after recoveries for R&W		1		0	(2)		3
(Paid) Recovered Losses After Recoveries for R&W	[2]	3		(2)	12		(2)
End of Period, Net Expected Loss to be Paid After Recoveries for R&W		96	[1]	(9)	96	[1]	(9)
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		802		646	821	[1]	661
Economic loss development after recoveries for R&W		(32)		(54)	(41)		(65)
(Paid) Recovered Losses After Recoveries for R&W	[2]	(22)		52	(32)		48
End of Period, Net Expected Loss to be Paid After Recoveries for R&W		853	[1]	$ 644	$ 853	[1]	$ 644
Radian [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		190
Radian [Member] | 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		85
Radian [Member] | 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		81
Radian [Member] | 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		4
Radian [Member] | 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		4
Radian [Member] | 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		3
Radian [Member] | 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		0
Radian [Member] | 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		7
Radian [Member] | 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		0
Radian [Member] | 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		(4)
Radian [Member] | 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		1
Radian [Member] | 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		0
Radian [Member] | 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		1
Radian [Member] | 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		0
Radian [Member] | 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		0
Radian [Member] | 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		0
Radian [Member] | 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		101
Radian [Member] | 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		$ 105

[1] Includes expected LAE to be paid of $15 million as of June 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 $5 million and $8 million in LAE for Second Quarter 2015 and 2014, respectively, and $9 million and $14 million in LAE for Six Months 2015 and 2014 , respectively.

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