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
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
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	$ 1,303	$ 1,198
Net expected loss to be paid on the MBIA UK portfolio as of January 10, 2017		21
Economic Loss Development / (Benefit)	(24)	47
Accretion of discount	8	8
Changes in discount rates	(6)	11
Changes in timing and assumptions	(26)	28
(Paid) Recovered Losses	19	(22)
End of Period, Net Expected Loss to be Paid After Recoveries for R&W	$ 1,298	1,244
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	2
Expected LAE to be paid	19		$ 23
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	1,203	904
Net expected loss to be paid on the MBIA UK portfolio as of January 10, 2017		13
Economic Loss Development / (Benefit)	(42)	119
(Paid) Recovered Losses	(111)	(25)
End of Period, Net Expected Loss to be Paid After Recoveries for R&W	1,050	1,011
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	1,157	871
Net expected loss to be paid on the MBIA UK portfolio as of January 10, 2017		0
Economic Loss Development / (Benefit)	(39)	124
(Paid) Recovered Losses	(111)	(25)
End of Period, Net Expected Loss to be Paid After Recoveries for R&W	1,007	970
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	46	33
Net expected loss to be paid on the MBIA UK portfolio as of January 10, 2017		13
Economic Loss Development / (Benefit)	(3)	(5)
(Paid) Recovered Losses	0	0
End of Period, Net Expected Loss to be Paid After Recoveries for R&W	43	41
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	73	206
Net expected loss to be paid on the MBIA UK portfolio as of January 10, 2017		0
Economic Loss Development / (Benefit)	16	(22)
(Paid) Recovered Losses	130	13
End of Period, Net Expected Loss to be Paid After Recoveries for R&W	219	197
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	123
Economic Loss Development / (Benefit)	(24)	(9)
End of Period, Net Expected Loss to be Paid After Recoveries for R&W	152
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	50
Economic Loss Development / (Benefit)	(8)	(13)
End of Period, Net Expected Loss to be Paid After Recoveries for R&W	67
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	27	88
Net expected loss to be paid on the MBIA UK portfolio as of January 10, 2017		8
Economic Loss Development / (Benefit)	2	(50)
(Paid) Recovered Losses	0	(10)
End of Period, Net Expected Loss to be Paid After Recoveries for R&W	29	36
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	100	294
Net expected loss to be paid on the MBIA UK portfolio as of January 10, 2017		8
Economic Loss Development / (Benefit)	18	(72)
(Paid) Recovered Losses	130	3
End of Period, Net Expected Loss to be Paid After Recoveries for R&W	248	233
MBIA UK Insurance Limited [Member]
Present Value of Net Expected Loss and Loss Adjustment Expenses to be Paid [Roll Forward]
Net expected loss to be paid on the MBIA UK portfolio as of January 10, 2017	$ 0	$ 21