Insurance Premiums (Roll Forward Of Premiums Receivable) (Detail) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2016	Dec. 31, 2015
Insurance Premiums [Abstract]
Premiums Receivable, Beginning balance	$ 792	$ 875
Premium Payments Received	(115)	(98)
Premiums from New Business Written	10	5
Adjustments, Changes in Expected Term of Policies	(5)	(16)
Adjustments, Accretion of Premiums Receivable Discount	19	21
Adjustments, Other	(292)	5
Premiums Receivable, Ending balance	$ 409	$ 792

No definition available.

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- Definition

Amount of new business written on financial guarantee insurance contracts.

+ References

No definition available.

+ Details

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- Definition

Amount of premium payments received during the period for premiums receivable on financial guarantee insurance contracts.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 310
-Section 50
-Paragraph 3
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=6933075&loc=SL5748726-161290

+ Details

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- Definition

This element represents the accretion of the discount for premiums receivable on financial guarantee insurance contracts.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 310
-Section 50
-Paragraph 3
-Subparagraph (c)(4)(iii)
-URI http://asc.fasb.org/extlink&oid=6933075&loc=SL5748726-161290

+ Details

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- Definition

This element represents adjustments to the premium receivable related to financial guarantee insurance contracts due to changes in the period of the contract.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 310
-Section 50
-Paragraph 3
-Subparagraph (c)(4)(i)
-URI http://asc.fasb.org/extlink&oid=6933075&loc=SL5748726-161290

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Period Type:	duration

- Definition

This element represents other adjustments to premiums receivable on financial guarantee insurance contracts.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 310
-Section 50
-Paragraph 3
-Subparagraph (c)(4)(iv)
-URI http://asc.fasb.org/extlink&oid=6933075&loc=SL5748726-161290

+ Details

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- Definition

The carrying amount as of the balance sheet date due the entity from (a) agents and insureds, (b) uncollected premiums and (c) others, net of the allowance for doubtful accounts.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.(a),5)
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

+ Details

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