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, 2016		Jun. 30, 2015	Jun. 30, 2016		Jun. 30, 2015	Dec. 31, 2015
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		$ 1,337		$ 1,154	$ 1,391	[1]	$ 1,169
Net expected loss to be paid on Radian Asset portfolio as of April 1, 2015				190			190
Economic loss development after recoveries for R&W		22		192	81		189
Accretion of discount		6		7	15		14
Changes in discount rates		45		(47)	108		(40)
Changes in timing and assumptions		(29)		232	(42)		215
(Paid) Recovered Losses After Recoveries for R&W	[2]	(33)		(26)	(146)		(38)
End of Period, Net Expected Loss to be Paid After Recoveries for R&W		1,326	[1]	1,510	$ 1,326	[1]	1,510
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		5	$ 9		9
Expected LAE to be paid		8			8			$ 12
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					1,391
Economic loss development after recoveries for R&W		22		192	81		189
End of Period, Net Expected Loss to be Paid After Recoveries for R&W		1,326			1,326
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		903		352	809	[1]	348
Net expected loss to be paid on Radian Asset portfolio as of April 1, 2015				85			85
Economic loss development after recoveries for R&W		109		224	208		230
(Paid) Recovered Losses After Recoveries for R&W	[2]	(12)		(4)	(17)		(6)
End of Period, Net Expected Loss to be Paid After Recoveries for R&W		1,000	[1]	657	1,000	[1]	657
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		864		310	771	[1]	303
Net expected loss to be paid on Radian Asset portfolio as of April 1, 2015				81			81
Economic loss development after recoveries for R&W		111		226	209		235
(Paid) Recovered Losses After Recoveries for R&W	[2]	(12)		(4)	(17)		(6)
End of Period, Net Expected Loss to be Paid After Recoveries for R&W		963	[1]	613	963	[1]	613
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		39		42	38	[1]	45
Net expected loss to be paid on Radian Asset portfolio as of April 1, 2015				4			4
Economic loss development after recoveries for R&W		(2)		(2)	(1)		(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		37	[1]	44	37	[1]	44
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		293		570	409	[1]	584
Net expected loss to be paid on Radian Asset portfolio as of April 1, 2015				4			4
Economic loss development after recoveries for R&W		(81)		(32)	(112)		(28)
(Paid) Recovered Losses After Recoveries for R&W	[2]	(20)		(18)	(105)		(36)
End of Period, Net Expected Loss to be Paid After Recoveries for R&W		192	[1]	524	192	[1]	524
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		228		569	348	[1]	595
Net expected loss to be paid on Radian Asset portfolio as of April 1, 2015				3			3
Economic loss development after recoveries for R&W		(74)		(26)	(110)		(28)
(Paid) Recovered Losses After Recoveries for R&W	[2]	(76)		(25)	(160)		(49)
End of Period, Net Expected Loss to be Paid After Recoveries for R&W		78	[1]	521	78	[1]	521
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)		3	(2)	[1]	4
Net expected loss to be paid on Radian Asset portfolio as of April 1, 2015				0			0
Economic loss development after recoveries for R&W		0		(1)	0		(1)
(Paid) Recovered Losses After Recoveries for R&W	[2]	4		(1)	5		(2)
End of Period, Net Expected Loss to be Paid After Recoveries for R&W		3	[1]	1	3	[1]	1
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		36		289	127	[1]	304
Net expected loss to be paid on Radian Asset portfolio as of April 1, 2015				7			7
Economic loss development after recoveries for R&W		(38)		(16)	(54)		(21)
(Paid) Recovered Losses After Recoveries for R&W	[2]	(94)		(15)	(169)		(25)
End of Period, Net Expected Loss to be Paid After Recoveries for R&W		(96)	[1]	265	(96)	[1]	265
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		(47)		(16)	(28)	[1]	(16)
Net expected loss to be paid on Radian Asset portfolio as of April 1, 2015				0			0
Economic loss development after recoveries for R&W		(10)		(3)	(31)		1
(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		(56)	[1]	(18)	(56)	[1]	(18)
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		240		293	251	[1]	303
Net expected loss to be paid on Radian Asset portfolio as of April 1, 2015				(4)			(4)
Economic loss development after recoveries for R&W		(26)		(6)	(25)		(7)
(Paid) Recovered Losses After Recoveries for R&W	[2]	13		(10)	1		(19)
End of Period, Net Expected Loss to be Paid After Recoveries for R&W		227	[1]	273	227	[1]	273
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		65		1	61	[1]	(11)
Net expected loss to be paid on Radian Asset portfolio as of April 1, 2015				1			1
Economic loss development after recoveries for R&W		(7)		(6)	(2)		0
(Paid) Recovered Losses After Recoveries for R&W	[2]	56		7	55		13
End of Period, Net Expected Loss to be Paid After Recoveries for R&W		114	[1]	3	114	[1]	3
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		102		165	99	[1]	161
Net expected loss to be paid on Radian Asset portfolio as of April 1, 2015				0			0
Economic loss development after recoveries for R&W		(2)		2	2		7
(Paid) Recovered Losses After Recoveries for R&W	[2]	0		(2)	(1)		(3)
End of Period, Net Expected Loss to be Paid After Recoveries for R&W		100	[1]	165	100	[1]	165
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		32		62	54	[1]	68
Net expected loss to be paid on Radian Asset portfolio as of April 1, 2015				0			0
Economic loss development after recoveries for R&W		(1)		1	(15)		(5)
(Paid) Recovered Losses After Recoveries for R&W	[2]	0		(5)	(8)		(5)
End of Period, Net Expected Loss to be Paid After Recoveries for R&W		31	[1]	58	31	[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		7		5	20	[1]	8
Net expected loss to be paid on Radian Asset portfolio as of April 1, 2015				101			101
Economic loss development after recoveries for R&W		(3)		(3)	(2)		(15)
(Paid) Recovered Losses After Recoveries for R&W	[2]	(1)		3	(15)		12
End of Period, Net Expected Loss to be Paid After Recoveries for R&W		3	[1]	106	3	[1]	106
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		434		802	582	[1]	821
Net expected loss to be paid on Radian Asset portfolio as of April 1, 2015				105			105
Economic loss development after recoveries for R&W		(87)		(32)	(127)		(41)
(Paid) Recovered Losses After Recoveries for R&W	[2]	(21)		(22)	(129)		(32)
End of Period, Net Expected Loss to be Paid After Recoveries for R&W		326	[1]	853	326	[1]	853
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)	$ 0		$ (190)

[1] Includes expected LAE to be paid of $8 million as of June 30, 2016 and $12 million as of December 31, 2015.

[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 $5 million in loss adjustment expenses ("LAE") for Second Quarter 2016 and 2015, respectively, and $9 million and $9 million in LAE for Six Months 2016 and 2015, respectively.