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Business Developments And Risks And Uncertainties (Narrative) (Detail) $ in Millions	6 Months Ended
	Jun. 30, 2016 USD ($)	Dec. 31, 2015 USD ($)
Business Acquisition [Line Items]
Number of operating segments	3
Cutwater sale effective date	Jan. 01, 2015
Mbia Inc [Member]
Business Acquisition [Line Items]
Liquid assets	$ 295	$ 416
Amount released from tax escrow account	105
Mbia Corp [Member] | Zohar [Member]
Business Acquisition [Line Items]
Insurance par exposure	772
National [Member] | Puerto Rico [Member]
Business Acquisition [Line Items]
Claims payments	$ 173

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This element represents the gross amount of claim payments during the period

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- Definition

This element represents the liquidity position of the entity

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- Definition

This element represents the amount released from the escrow account related to the tax sharing agreement during the period

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No definition available.

+ Details

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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- Definition

Date the entity disposed of a business or a group of assets, in CCYY-MM-DD format.

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- Definition

Maximum potential amount of future payments (undiscounted) the guarantor could be required to make under the guarantee or each group of similar guarantees before reduction for potential recoveries under recourse or collateralization provisions.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=6851643&loc=d3e12069-110248

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- Definition

Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.

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