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Financial Guarantee Insurance Contracts - Summary of Information Related to Policies Currently Included in Ambac's Loss Reserves or Subrogation Recoverable (Detail) - Successor [Member] $ in Thousands | 9 Months Ended | 12 Months Ended |  |
--- | --- | --- | --- | ---
Sep. 30, 2015 USD ($) Policies | Dec. 31, 2014 USD ($) Policies | Sep. 30, 2014 USD ($) | Dec. 31, 2013 USD ($)
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items] |  |  |  |
Number of policies | Policies | 323 | 325 |  |
Remaining weighted-average contract period (in years) | 16 years | 16 years |  |
Gross insured contractual payments outstanding: |  |  |  |
Principal | $ 16,609,211 | $ 18,322,914 |  |
Interest | 6,012,061 | 7,254,995 |  |
Total | 22,621,272 | 25,577,909 |  |
Gross undiscounted claim liability | 7,856,763 | 8,679,974 |  |
Discount, gross claim liability | 1,241,288 | 1,509,948 |  |
Gross claim liability before all subrogation and before reinsurance | 6,615,475 | 7,170,026 |  |
Less: |  |  |  |
Gross RMBS subrogation | (2,569,094) | (2,541,219) |  |
Discount, RMBS subrogation | 13,633 | 17,679 |  |
Discounted RMBS subrogation, before reinsurance | (2,555,461) | (2,523,540) | $ (2,214,430) | $ (2,206,598)
Less: |  |  |  |
Gross other subrogation | (801,390) | (792,287) |  |
Discount, other subrogation | 76,723 | 91,808 |  |
Discounted other subrogation, before reinsurance | (724,667) | (700,479) |  |
Gross claim liability, net of all subrogation and discounts, before reinsurance | 3,335,347 | 3,946,007 |  |
Less: Unearned premium reserves | (179,120) | (241,348) |  |
Plus: Loss adjustment expenses reserves | 99,086 | 94,074 |  |
Claim liability reported on Balance Sheet, before reinsurance | 3,255,313 | 3,798,733 |  |
Reinsurance recoverable reported on Balance Sheet | $ 68,319 | $ 99,838 |  |
I/SL [Member] |  |  |  |
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items] |  |  |  |
Number of policies | Policies | 44 | 36 |  |
Remaining weighted-average contract period (in years) | 7 years | 8 years |  |
Gross insured contractual payments outstanding: |  |  |  |
Principal | $ 2,099,540 | $ 1,026,513 |  |
Interest | 730,755 | 418,746 |  |
Total | 2,830,295 | 1,445,259 |  |
Gross undiscounted claim liability | 15,820 | 16,360 |  |
Discount, gross claim liability | 786 | 1,147 |  |
Gross claim liability before all subrogation and before reinsurance | 15,034 | 15,213 |  |
Less: |  |  |  |
Gross RMBS subrogation | 0 | 0 |  |
Discount, RMBS subrogation | 0 | 0 |  |
Discounted RMBS subrogation, before reinsurance | 0 | 0 |  |
Less: |  |  |  |
Gross other subrogation | 0 | 0 |  |
Discount, other subrogation | 0 | 0 |  |
Discounted other subrogation, before reinsurance | 0 | 0 |  |
Gross claim liability, net of all subrogation and discounts, before reinsurance | 15,034 | 15,213 |  |
Less: Unearned premium reserves | (10,207) | (10,945) |  |
Plus: Loss adjustment expenses reserves | 0 | 3 |  |
Claim liability reported on Balance Sheet, before reinsurance | 4,827 | 4,271 |  |
Reinsurance recoverable reported on Balance Sheet | $ 641 | $ 73 |  |
IA [Member] |  |  |  |
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items] |  |  |  |
Number of policies | Policies | 17 | 26 |  |
Remaining weighted-average contract period (in years) | 17 years | 12 years |  |
Gross insured contractual payments outstanding: |  |  |  |
Principal | $ 305,681 | $ 519,291 |  |
Interest | 138,831 | 212,296 |  |
Total | 444,512 | 731,587 |  |
Gross undiscounted claim liability | 6,036 | 11,525 |  |
Discount, gross claim liability | 596 | 937 |  |
Gross claim liability before all subrogation and before reinsurance | 5,440 | 10,588 |  |
Less: |  |  |  |
Gross RMBS subrogation | 0 | 0 |  |
Discount, RMBS subrogation | 0 | 0 |  |
Discounted RMBS subrogation, before reinsurance | 0 | 0 |  |
Less: |  |  |  |
Gross other subrogation | 0 | 0 |  |
Discount, other subrogation | 0 | 0 |  |
Discounted other subrogation, before reinsurance | 0 | 0 |  |
Gross claim liability, net of all subrogation and discounts, before reinsurance | 5,440 | 10,588 |  |
Less: Unearned premium reserves | (2,089) | (3,432) |  |
Plus: Loss adjustment expenses reserves | 80 | 1,303 |  |
Claim liability reported on Balance Sheet, before reinsurance | 3,431 | 8,459 |  |
Reinsurance recoverable reported on Balance Sheet | $ 895 | $ 890 |  |
II [Member] |  |  |  |
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items] |  |  |  |
Number of policies | Policies | 30 | 33 |  |
Remaining weighted-average contract period (in years) | 14 years | 15 years |  |
Gross insured contractual payments outstanding: |  |  |  |
Principal | $ 1,338,428 | $ 3,091,744 |  |
Interest | 356,410 | 1,878,770 |  |
Total | 1,694,838 | 4,970,514 |  |
Gross undiscounted claim liability | 46,817 | 155,488 |  |
Discount, gross claim liability | 12,179 | 16,438 |  |
Gross claim liability before all subrogation and before reinsurance | 34,638 | 139,050 |  |
Less: |  |  |  |
Gross RMBS subrogation | 0 | 0 |  |
Discount, RMBS subrogation | 0 | 0 |  |
Discounted RMBS subrogation, before reinsurance | 0 | 0 |  |
Less: |  |  |  |
Gross other subrogation | (12,719) | (18,034) |  |
Discount, other subrogation | 3,538 | 6,069 |  |
Discounted other subrogation, before reinsurance | (9,181) | (11,965) |  |
Gross claim liability, net of all subrogation and discounts, before reinsurance | 25,457 | 127,085 |  |
Less: Unearned premium reserves | (17,961) | (73,749) |  |
Plus: Loss adjustment expenses reserves | 819 | 1,968 |  |
Claim liability reported on Balance Sheet, before reinsurance | 8,315 | 55,304 |  |
Reinsurance recoverable reported on Balance Sheet | $ 67 | $ 1,355 |  |
III [Member] |  |  |  |
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items] |  |  |  |
Number of policies | Policies | 65 | 69 |  |
Remaining weighted-average contract period (in years) | 19 years | 21 years |  |
Gross insured contractual payments outstanding: |  |  |  |
Principal | $ 3,913,273 | $ 3,792,559 |  |
Interest | 2,940,877 | 2,765,537 |  |
Total | 6,854,150 | 6,558,096 |  |
Gross undiscounted claim liability | 1,639,016 | 2,040,402 |  |
Discount, gross claim liability | 524,462 | 716,812 |  |
Gross claim liability before all subrogation and before reinsurance | 1,114,554 | 1,323,590 |  |
Less: |  |  |  |
Gross RMBS subrogation | 0 | 0 |  |
Discount, RMBS subrogation | 0 | 0 |  |
Discounted RMBS subrogation, before reinsurance | 0 | 0 |  |
Less: |  |  |  |
Gross other subrogation | (133,640) | (127,143) |  |
Discount, other subrogation | 35,910 | 36,779 |  |
Discounted other subrogation, before reinsurance | (97,730) | (90,364) |  |
Gross claim liability, net of all subrogation and discounts, before reinsurance | 1,016,824 | 1,233,226 |  |
Less: Unearned premium reserves | (86,842) | (88,332) |  |
Plus: Loss adjustment expenses reserves | 18,708 | 6,470 |  |
Claim liability reported on Balance Sheet, before reinsurance | 948,690 | 1,151,364 |  |
Reinsurance recoverable reported on Balance Sheet | $ 82,496 | $ 110,957 |  |
IV [Member] |  |  |  |
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items] |  |  |  |
Number of policies | Policies | 164 | 160 |  |
Remaining weighted-average contract period (in years) | 14 years | 12 years |  |
Gross insured contractual payments outstanding: |  |  |  |
Principal | $ 8,897,699 | $ 9,892,760 |  |
Interest | 1,827,031 | 1,979,627 |  |
Total | 10,724,730 | 11,872,387 |  |
Gross undiscounted claim liability | 6,076,327 | 6,456,139 |  |
Discount, gross claim liability | 697,119 | 774,611 |  |
Gross claim liability before all subrogation and before reinsurance | 5,379,208 | 5,681,528 |  |
Less: |  |  |  |
Gross RMBS subrogation | (2,569,094) | (2,541,219) |  |
Discount, RMBS subrogation | 13,633 | 17,679 |  |
Discounted RMBS subrogation, before reinsurance | (2,555,461) | (2,523,540) |  |
Less: |  |  |  |
Gross other subrogation | (641,812) | (647,110) |  |
Discount, other subrogation | 33,468 | 48,960 |  |
Discounted other subrogation, before reinsurance | (608,344) | (598,150) |  |
Gross claim liability, net of all subrogation and discounts, before reinsurance | 2,215,403 | 2,559,838 |  |
Less: Unearned premium reserves | (61,546) | (64,890) |  |
Plus: Loss adjustment expenses reserves | 79,479 | 84,330 |  |
Claim liability reported on Balance Sheet, before reinsurance | 2,233,336 | 2,579,278 |  |
Reinsurance recoverable reported on Balance Sheet | $ (15,780) | $ (13,437) |  |
V [Member] |  |  |  |
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items] |  |  |  |
Number of policies | Policies | 3 | 1 |  |
Remaining weighted-average contract period (in years) | 6 years | 6 years |  |
Gross insured contractual payments outstanding: |  |  |  |
Principal | $ 54,590 | $ 47 |  |
Interest | 18,157 | 19 |  |
Total | 72,747 | 66 |  |
Gross undiscounted claim liability | 72,747 | 60 |  |
Discount, gross claim liability | 6,146 | 3 |  |
Gross claim liability before all subrogation and before reinsurance | 66,601 | 57 |  |
Less: |  |  |  |
Gross RMBS subrogation | 0 | 0 |  |
Discount, RMBS subrogation | 0 | 0 |  |
Discounted RMBS subrogation, before reinsurance | 0 | 0 |  |
Less: |  |  |  |
Gross other subrogation | (13,219) | 0 |  |
Discount, other subrogation | 3,807 | 0 |  |
Discounted other subrogation, before reinsurance | (9,412) | 0 |  |
Gross claim liability, net of all subrogation and discounts, before reinsurance | 57,189 | 57 |  |
Less: Unearned premium reserves | (475) | 0 |  |
Plus: Loss adjustment expenses reserves | 0 | 0 |  |
Claim liability reported on Balance Sheet, before reinsurance | 56,714 | 57 |  |
Reinsurance recoverable reported on Balance Sheet | $ 0 | $ 0 |  |

X
- Definition Discounted other subrogation, before reinsurance. + References No definition available. + Details
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Balance Type: | na
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- Definition Less Discounted Rmbs Subrogation Before Reinsurance [Abstract] + References No definition available. + Details
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Namespace Prefix: | ambc_
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- Definition This element represents the discounting on the gross claim liability for financial guarantee insurance contracts presented in the context of each surveillance grouping or category used by management to monitor and track potential deterioration in the credit worthiness of the insured party's ability to meet its financial obligations related to the contracts underlying financial guarantee insurance contracts the entity has issued. + References No definition available. + Details
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Namespace Prefix: | ambc_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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- Definition This element represents the gross undiscounted claim liability for financial guarantee insurance contracts presented in the context of each surveillance grouping or category used by management to monitor and track potential deterioration in the credit worthiness of the insured party's ability to meet its financial obligations related to the contracts underlying financial guarantee insurance contracts the entity has issued. + References No definition available. + Details
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Namespace Prefix: | ambc_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition This element represents the amount of loss adjustment expense reserves represent the costs estimated to be incurred in the settlement of unpaid claims related to financial guarantee insurance contracts and presented in the schedule of insured financial obligations with credit deterioration in the context of each surveillance grouping or category used by management to monitor and track potential deterioration in the credit worthiness of the insured party's ability to meet its financial obligations related to the contracts underlying financial guarantee insurance contracts the entity has issued. + References No definition available. + Details
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Namespace Prefix: | ambc_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition This element represents the discount on the gross subrogation on insured financial obligations with credit deterioration, excluding the discount on the gross subrogation on insured RMBS financial obligations with credit deterioration. + References No definition available. + Details
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Namespace Prefix: | ambc_
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Balance Type: | debit
Period Type: | instant

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- Definition This element represents the discounting on the reduction to gross claim liability for subrogation on insured RMBS financial obligations with credit deterioration. + References No definition available. + Details
Name: | ambc_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationReductionsOfGrossClaimLiabilityDiscountOnRmbsSubrogation
Namespace Prefix: | ambc_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
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- Definition This element represents the reduction to gross claim liability for subrogation on insured financial obligations with credit deterioration, excluding the reduction to gross claim liability for subrogation on insured RMBS financial obligations with credit deterioration. + References No definition available. + Details
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Namespace Prefix: | ambc_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition This element represents the reduction to gross claim liability for subrogation on insured RMBS financial obligations with credit deterioration. + References No definition available. + Details
Name: | ambc_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationReductionsOfGrossClaimLiabilityRmbsSubrogation
Namespace Prefix: | ambc_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Definition This element represents the reduction to gross undiscounted claim liability for gross undiscounted subrogation on insured financial obligations with credit deterioration, excluding subrogation on insured RMBS financial obligations with credit deterioration. + References No definition available. + Details
Name: | ambc_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationReductionsOfGrossUndiscountedClaimLiabilityGrossUndiscountedOtherSubrogation
Namespace Prefix: | ambc_
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X
- Definition This element represents the reduction to gross undiscounted claim liability for gross undiscounted subrogation on insured RMBS financial obligations with credit deterioration. + References No definition available. + Details
Name: | ambc_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationReductionsOfGrossUndiscountedClaimLiabilityGrossUndiscountedRmbsSubrogation
Namespace Prefix: | ambc_
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X
- Definition Remaining weighted average contract period of financial guarantee insurance contracts, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 9 -Subparagraph (a)(5)(ii) -URI http://asc.fasb.org/extlink&oid=6933314&loc=SL5749324-161292 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 55 -Paragraph 32 -URI http://asc.fasb.org/extlink&oid=34726416&loc=SL5751133-161288 + Details
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X
- Definition This element represents the gross claim liability for financial guarantee insurance contracts presented in the context of each surveillance grouping or category used by management to monitor and track potential deterioration in the credit worthiness of the insured party's ability to meet its financial obligations related to the contracts underlying financial guarantee insurance contracts the entity has issued. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 55 -Paragraph 32 -URI http://asc.fasb.org/extlink&oid=34726416&loc=SL5751133-161288 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 9 -Subparagraph (a)(5)(iv) -URI http://asc.fasb.org/extlink&oid=6933314&loc=SL5749324-161292 + Details
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X
- Definition This element represents the amount of insured contractual payments outstanding on the underlying insured obligations for financial guarantee insurance contracts presented in the context of each surveillance grouping or category used by management to monitor and track potential deterioration in the credit worthiness of the insured party's ability to meet its financial obligations related to the contracts underlying financial guarantee insurance contracts the entity has issued. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 55 -Paragraph 32 -URI http://asc.fasb.org/extlink&oid=34726416&loc=SL5751133-161288 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 9 -Subparagraph (a)(5)(iii) -URI http://asc.fasb.org/extlink&oid=6933314&loc=SL5749324-161292 + Details
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- References No definition available. + Details
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- Definition This element represents the amount of insured contractual payments outstanding attributable to interest accrued on the underlying insured obligations for financial guarantee insurance contracts presented in the context of each surveillance grouping or category used by management to monitor and track potential deterioration in the credit worthiness of the insured party's ability to meet its financial obligations related to the contracts underlying financial guarantee insurance contracts the entity has issued. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 55 -Paragraph 32 -URI http://asc.fasb.org/extlink&oid=34726416&loc=SL5751133-161288 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 9 -Subparagraph (a)(5)(iii) -URI http://asc.fasb.org/extlink&oid=6933314&loc=SL5749324-161292 + Details
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X
- Definition This element represents the amount of insured contractual payments outstanding attributable to the principal of the underlying insured obligations for financial guarantee insurance contracts presented in the context of each surveillance grouping or category used by management to monitor and track potential deterioration in the credit worthiness of the insured party's ability to meet its financial obligations related to the contracts underlying financial guarantee insurance contracts the entity has issued. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 9 -Subparagraph (a)(5)(iii) -URI http://asc.fasb.org/extlink&oid=6933314&loc=SL5749324-161292 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 55 -Paragraph 32 -URI http://asc.fasb.org/extlink&oid=34726416&loc=SL5751133-161288 + Details
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X
- 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. + References No definition available. + Details
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X
- Definition This element represents the net claim liability related to financial guarantee insurance contracts presented in the context of each surveillance grouping or category used by management to monitor and track potential deterioration in the credit worthiness of the insured party's ability to meet its financial obligations related to the contracts underlying financial guarantee insurance contracts the entity has issued. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 55 -Paragraph 32 -URI http://asc.fasb.org/extlink&oid=34726416&loc=SL5751133-161288 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 9 -Subparagraph (a)(5)(vii) -URI http://asc.fasb.org/extlink&oid=6933314&loc=SL5749324-161292 + Details
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X
- Definition This element represents the number of issued and outstanding contracts for each surveillance grouping or category used by management to monitor and track potential deterioration in the credit worthiness of the insured party's ability to meet its financial obligations related to the contracts underlying financial guarantee insurance contracts the entity has issued. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 9 -Subparagraph (a)(5)(i) -URI http://asc.fasb.org/extlink&oid=6933314&loc=SL5749324-161292 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 55 -Paragraph 32 -URI http://asc.fasb.org/extlink&oid=34726416&loc=SL5751133-161288 + Details
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X
- Definition This element represents the claim liability, reported on or included in the statement of financial position, related to financial guarantee insurance contracts and presented in the schedule of insured financial obligations with credit deterioration in the context of each surveillance grouping or category used by management to monitor and track potential deterioration in the credit worthiness of the insured party's ability to meet its financial obligations related to the contracts underlying financial guarantee insurance contracts the entity has issued. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 55 -Paragraph 34 -URI http://asc.fasb.org/extlink&oid=34726416&loc=SL5751140-161288 + Details
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X
- Definition This element represents the amount of reinsurance recoverable, reported on or included in the statement of financial position, related to financial guarantee insurance contracts and presented in the schedule of insured financial obligations with credit deterioration in the context of each surveillance grouping or category used by management to monitor and track potential deterioration in the credit worthiness of the insured party's ability to meet its financial obligations related to the contracts underlying financial guarantee insurance contracts the entity has issued. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 9 -Subparagraph (a)(5)(viii) -URI http://asc.fasb.org/extlink&oid=6933314&loc=SL5749324-161292 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 55 -Paragraph 32 -URI http://asc.fasb.org/extlink&oid=34726416&loc=SL5751133-161288 + Details
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- Definition This element represents the amount of unearned premium revenue, reported on or included in the statement of financial position, related to financial guarantee insurance contracts and presented in the schedule of insured financial obligations with credit deterioration in the context of each surveillance grouping or category used by management to monitor and track potential deterioration in the credit worthiness of the insured party's ability to meet its financial obligations related to the contracts underlying financial guarantee insurance contracts the entity has issued. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 55 -Paragraph 32 -URI http://asc.fasb.org/extlink&oid=34726416&loc=SL5751133-161288 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 9 -Subparagraph (a)(5)(ix) -URI http://asc.fasb.org/extlink&oid=6933314&loc=SL5749324-161292 + Details
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Period Type: | instant

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