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		Dec. 31, 2016	Dec. 31, 2015
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
Assets held for sale		$ 555
Variable Interest Entity Primary Beneficiary [Member]
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items]
Investments held-to-maturity, fair value		876	$ 2,401
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]
Total assets		0	0
Total liabilities		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		2
Accrued investment income	[1]	40	38
Receivable for investments sold	[1]		26
Assets held for sale		306
Total assets		348	64
Long-term debt		1,030	762
Payable for investments purchased	[2]	32	36
Total liabilities		1,062	798
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			3
Total assets		876	2,404
Investment agreements		508	595
Medium-term notes		478	534
Total liabilities		1,868	3,725
Gross		2,638	3,093
Ceded		18	94
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]
Investments held-to-maturity, fair value		876	2,401
Variable interest entity notes		882	2,596
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		3	3
Accrued investment income	[1]	40	38
Receivable for investments sold	[1]		26
Assets held for sale		306
Total assets		1,239	2,756
Investment agreements		399	462
Medium-term notes		794	855
Long-term debt		1,986	1,889
Payable for investments purchased	[2]	32	36
Total liabilities		4,101	5,931
Gross		995	1,530
Ceded		43	56
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]
Investments held-to-maturity, fair value		890	2,689
Variable interest entity notes		890	2,689
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		2	3
Accrued investment income	[1]	40	38
Receivable for investments sold	[1]		26
Assets held for sale		306
Total assets		1,224	2,468
Investment agreements		508	595
Medium-term notes		478	534
Long-term debt		1,030	762
Payable for investments purchased	[2]	32	36
Total liabilities		2,930	4,523
Gross		2,638	3,093
Ceded		18	94
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]
Investments held-to-maturity, fair value		876	2,401
Variable interest entity notes		$ 882	$ 2,596

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

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