Fair Value Measurement (Fair Value Hierarchy Table Presents The Company's Assets And Liabilities At Fair Value Not Recorded On The Company's Consolidated Balance Sheet) (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012		Dec. 31, 2011
Variable Interest Entity [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Variable interest entity notes	$ 7,227		$ 8,697
Long-term debt			360
Value Disclosed At Fair Value Not Recorded At Fair Value [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Other investments	11		11
Accrued investment income	57	[1]	63	[1]
Receivable for investments sold	60	[1]	32	[1]
Total assets	3,024		3,595
Investment agreements	1,445		1,853
Medium-term notes	982		1,187
Long-term debt	1,119		286
Long-term debt	43	[2]	1,117
Payable for investments purchased			3	[2]
Total liabilities	6,805		8,111
Gross	975		1,451
Ceded	92		94
Value Disclosed At Fair Value Not Recorded At Fair Value [Member] | Variable Interest Entity [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Variable interest entity notes	3,216		3,297
Investments held-to-maturity	2,896		3,489
Long-term debt			368
Value Disclosed At Fair Value Not Recorded At Fair Value [Member] | Quoted Prices In Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Accrued investment income	57	[1]	63	[1]
Receivable for investments sold	60	[1]	32	[1]
Total assets	117		95
Long-term debt	43	[2]
Payable for investments purchased			3	[2]
Total liabilities	43		3
Value Disclosed At Fair Value Not Recorded At Fair Value [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Long-term debt	1,119		286
Long-term debt			1,117
Total liabilities	1,119		1,403
Value Disclosed At Fair Value Not Recorded At Fair Value [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Other investments	11		11
Total assets	2,907		3,500
Investment agreements	1,445		1,853
Medium-term notes	982		1,187
Total liabilities	5,643		6,705
Gross	975		1,451
Ceded	92		94
Value Disclosed At Fair Value Not Recorded At Fair Value [Member] | Significant Unobservable Inputs (Level 3) [Member] | Variable Interest Entity [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Variable interest entity notes	3,216		3,297
Investments held-to-maturity	2,896		3,489
Long-term debt			368
Carrying Value [Member] | Value Disclosed At Fair Value Not Recorded At Fair Value [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Other investments	11		11
Accrued investment income	57	[1]	63	[1]
Receivable for investments sold	60	[1]	32	[1]
Total assets	3,179		3,949
Investment agreements	1,171		1,578
Medium-term notes	1,415		1,491
Long-term debt	1,837		287
Long-term debt	43	[2]	1,840
Payable for investments purchased			3	[2]
Total liabilities	8,055		9,502
Gross	831		1,305
Ceded	95		104
Carrying Value [Member] | Value Disclosed At Fair Value Not Recorded At Fair Value [Member] | Variable Interest Entity [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Variable interest entity notes	3,589		3,943
Investments held-to-maturity	3,051		3,843
Long-term debt			$ 360

[1] Reported within "Other assets" on MBIA's consolidated balance sheets.

[2] Reported within "Other liabilities" on MBIA's consolidated balance sheets.