Contracts Accounted for as Insurance - Components of Unearned Premium Reserve (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Insurance [Abstract]
Deferred premium revenue, gross	$ 3,647	$ 3,548
Deferred premium revenue, ceded	107	206
Deferred premium revenue, net	3,540	3,342
Contra-paid, gross	(50)	(37)
Contra-paid, ceded	1	0
Contra-paid, net	(51)	(37)
Unearned premium reserve, gross	3,597	3,511
Unearned premium reserve, ceded	108	206
Unearned premium reserve, net	3,489	3,305
Total net unearned premium reserve related to FG VIE	79	90
Contra-paid related to FG VIE	18	$ 25
Financial Guarantee Contracts, Other Deferred Premium Revenue	$ 7

Financial Guarantee Contracts, Other Deferred Premium Revenue

No definition available.

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- Definition

Amount of losses paid and not yet expensed on financial guaranty insurance contracts, ceded amounts.

+ References

No definition available.

+ Details

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- Definition

Amount of losses paid and not yet expensed on financial guaranty insurance contracts, gross amounts.

+ References

No definition available.

+ Details

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- Definition

Amount of losses paid and not yet expensed on financial guaranty insurance contracts, net of ceded amounts.

+ References

No definition available.

+ Details

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- Definition

Amount of losses paid and not yet expensed on financial guaranty insurance contracts related to variable interest entities.

+ References

No definition available.

+ Details

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- Definition

The unexpired portion of premiums ceded on financial guaranty insurance policies in force as of the balance sheet date before adjustment for prepaid losses.

+ References

No definition available.

+ Details

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- Definition

Amount of unearned premium revenue in the statement of financial position for financial guarantee insurance contracts before adjustment for prepaid losses.

+ References

No definition available.

+ Details

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- Definition

Amount of unearned premium revenue in the statement of financial position for financial guaranty insurance contracts, net of the unexpired portion of premiums ceded and before adjustment for loss claims paid but not yet expensed.

+ References

No definition available.

+ Details

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- Definition

Carrying amount of premiums written on insurance contracts that have not been earned, net of the unexpired portion of premiums ceded on policies in force as of the balance sheet date.

+ References

No definition available.

+ Details

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- Definition

Represents the carrying amount of premiums written on insurance contracts that have not been earned, net of the unexpired portion of premiums ceded on policies in force as of the balance sheet date which are related to variable interest entity.

+ References

No definition available.

+ Details

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- References

No definition available.

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- Definition

The unexpired portion of premiums ceded on policies in force as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 340
-Section 25
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6485982&loc=d3e22818-158507

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- Definition

Carrying amount of premiums written on insurance contracts that have not been earned as of the balance sheet date.

+ 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)(13)(a)(2))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 235
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-16(Column D))
-URI http://asc.fasb.org/extlink&oid=34713774&loc=d3e574960-122915

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