Consolidated Balance Sheets (USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Assets
Cash and cash equivalents	$ 1,103	$ 990
Deferred income taxes, net	1,200
Investments held-to-maturity, at amortized cost (fair value $2,566 and $2,674)	2,809	2,829
Total assets	17,633	21,724
Liabilities:
Total liabilities	14,432	18,530
Commitments and contingencies (See Note 14)
Equity:
Preferred stock, par value $1 per share; authorized shares--10,000,000; issued and outstanding--none	0	0
Common stock, par value $1 per share; authorized shares--400,000,000; issued shares--277,804,062 and 277,405,039	278	277
Additional paid-in capital	3,113	3,076
Retained earnings	2,157	2,039
Accumulated other comprehensive income (loss), net of tax of $30 and $21	(50)	56
Treasury stock, at cost--85,551,418 and 81,733,530 shares	(2,318)	(2,275)
Total shareholders' equity of MBIA Inc.	3,180	3,173
Preferred stock of subsidiary and noncontrolling interest	21	21
Total equity	3,201	3,194
Total liabilities and equity	17,633	21,724
Non Variable Interest Entity [Member]
Assets
Fixed-maturity securities held as available-for-sale, at fair value (amortized cost $4,516 and $4,347)Investments held as available-for-sale, at fair value (amortized cost $156 and $637)	4,505	4,485
Fixed-maturity securities at fair value	249	244
Investments pledged as collateral, at fair value (amortized cost $407 and $489)	347	443
Short-term investments held as available-for-sale, at fair value (amortized cost $1,377 and $662)	1,378	669
Other investments (includes investments at fair value of $10 and $12)	16	21
Total investments	6,495	5,862
Cash and cash equivalents	1,057	814
Premiums receivable	1,085	1,228
Deferred acquisition costs	270	302
Insurance loss recoverable	742	3,648
Property and equipment, at cost (less accumulated depreciation of $87 and $146)	37	69
Deferred income taxes, net	1,243	1,199
Other assets	247	268
Liabilities:
Unearned premium revenue	2,544	2,938
Loss and loss adjustment expense reserves	688	853
Investment agreements	760	944
Medium-term notes (includes financial instruments carried at fair value of $204 and $165)	1,554	1,598
Long-term debt	1,677	1,732
Derivative liabilities	1,370	2,934
Other liabilities	439	245
Variable Interest Entity Primary Beneficiary [Member]
Assets
Fixed-maturity securities held as available-for-sale, at fair value (amortized cost $4,516 and $4,347)Investments held as available-for-sale, at fair value (amortized cost $156 and $637)	156	625
Fixed-maturity securities at fair value	626	1,735
Other assets	0	2
Cash	46	176
Investments held-to-maturity, at amortized cost (fair value $2,566 and $2,674)	2,809	2,829
Loans receivable at fair value	1,704	1,881
Loan repurchase commitments	1,116	1,086
Liabilities:
Derivative liabilities	15	162
Variable interest entity notes (includes financial instruments carried at fair value of $2,426 and $3,659)	$ 5,385	$ 7,124