Related Party Transactions (Narrative) (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2013
Related Party Transactions [Abstract]
Principal ownership percentage	10.00%
Number of executed surety bonds	5
Surety bonds maximum exposure	$ 340
Number of loans to executive officers or directors	0

Number of surety bonds executed to guarantee the payment obligations of the members of the Municipal Bond Insurance Association.

No definition available.

Name:	mbi_NumberOfSuretyBonds
Namespace Prefix:	mbi_
Data Type:	xbrli:positiveIntegerItemType
Balance Type:	na
Period Type:	duration