Fair Value Of Financial Instruments (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, 2014		Dec. 31, 2013
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
Investments held-to-maturity, fair value	$ 2,780		$ 2,651
Value Disclosed At Fair Value Not Recorded At Fair Value [Member] | Fair Value Inputs Level 1 [Member]
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
Other investments	0		0
Accrued investment income	0	[1]	0	[1]
Receivable for investments sold	0	[1]	0	[1]
Net cash collateral pledged	0	[1]	24	[1]
Total assets	0		24
Investment agreements	0		0
Medium-term notes	0		0
Securities Loaned Or Sold Under Agreements To Repurchase	0		0
Long-term debt	0		0
Payable for investments purchased	0	[2]	0	[2]
Secured loan	0
Total liabilities	0		0
Gross	0		0
Ceded	0		0
Value Disclosed At Fair Value Not Recorded At Fair Value [Member] | Fair Value Inputs Level 1 [Member] | Variable Interest Entity Primary Beneficiary [Member]
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
Variable interest entity notes	0		0
Investments held-to-maturity, fair value	0		0
Value Disclosed At Fair Value Not Recorded At Fair Value [Member] | Fair Value Inputs Level 2 [Member]
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
Other investments	0		0
Accrued investment income	51	[1]	52	[1]
Receivable for investments sold	75	[1]	22	[1]
Net cash collateral pledged	0	[1]	0	[1]
Total assets	126		74
Investment agreements	0		0
Medium-term notes	0		0
Securities Loaned Or Sold Under Agreements To Repurchase	0		0
Long-term debt	1,516		1,412
Payable for investments purchased	34	[2]	31	[2]
Secured loan	0
Total liabilities	1,550		1,443
Gross	0		0
Ceded	0		0
Value Disclosed At Fair Value Not Recorded At Fair Value [Member] | Fair Value Inputs Level 2 [Member] | Variable Interest Entity Primary Beneficiary [Member]
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
Variable interest entity notes	0		0
Investments held-to-maturity, fair value	0		0
Value Disclosed At Fair Value Not Recorded At Fair Value [Member] | Fair Value Inputs Level 3 [Member]
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
Other investments	4		4
Accrued investment income	0	[1]	0	[1]
Receivable for investments sold	0	[1]	0	[1]
Net cash collateral pledged	0	[1]	0	[1]
Total assets	2,784		2,655
Investment agreements	801		814
Medium-term notes	832		927
Securities Loaned Or Sold Under Agreements To Repurchase	0		0
Long-term debt	0		0
Payable for investments purchased	0	[2]	0	[2]
Secured loan	0
Total liabilities	4,413		4,492
Gross	4,487		2,843
Ceded	116		71
Value Disclosed At Fair Value Not Recorded At Fair Value [Member] | Fair Value Inputs Level 3 [Member] | Variable Interest Entity Primary Beneficiary [Member]
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
Variable interest entity notes	2,780		2,751
Investments held-to-maturity, fair value	2,780		2,651
Carrying Reported Amount Fair Value Disclosure [Member] | Value Disclosed At Fair Value Not Recorded At Fair Value [Member]
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
Other investments	4		5
Accrued investment income	51	[1]	52	[1]
Receivable for investments sold	75	[1]	22	[1]
Net cash collateral pledged	0	[1]	24	[1]
Total assets	2,917		2,904
Investment agreements	660		700
Medium-term notes	1,069		1,224
Securities Loaned Or Sold Under Agreements To Repurchase	0		0
Long-term debt	1,755		1,702
Payable for investments purchased	34	[2]	31	[2]
Secured loan	0
Total liabilities	6,305		6,587
Gross	2,181		2,388
Ceded	72		76
Carrying Reported Amount Fair Value Disclosure [Member] | Value Disclosed At Fair Value Not Recorded At Fair Value [Member] | Variable Interest Entity Primary Beneficiary [Member]
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
Variable interest entity notes	2,787		2,930
Investments held-to-maturity, fair value	2,787		2,801
Fair 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	4		4
Accrued investment income	51	[1]	52	[1]
Receivable for investments sold	75	[1]	22	[1]
Net cash collateral pledged	0	[1]	24	[1]
Total assets	2,910		2,753
Investment agreements	801		814
Medium-term notes	832		927
Securities Loaned Or Sold Under Agreements To Repurchase	0		0
Long-term debt	1,516		1,412
Payable for investments purchased	34	[2]	31	[2]
Secured loan	0
Total liabilities	5,963		5,935
Gross	4,487		2,843
Ceded	116		71
Fair Value [Member] | Value Disclosed At Fair Value Not Recorded At Fair Value [Member] | Variable Interest Entity Primary Beneficiary [Member]
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
Variable interest entity notes	2,780		2,751
Investments held-to-maturity, fair value	$ 2,780		$ 2,651

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

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