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Financial Guarantee Insurance Contracts - Additional Information (Detail) £ in Thousands, $ in Thousands | 3 Months Ended | 12 Months Ended |  |  |  |
--- | --- | --- | --- | --- | --- | ---
Dec. 31, 2018 USD ($) | Sep. 30, 2018 USD ($) | Jun. 30, 2018 USD ($) | Mar. 31, 2018 USD ($) | Dec. 31, 2017 USD ($) | Sep. 30, 2017 USD ($) | Jun. 30, 2017 USD ($) | Mar. 31, 2017 USD ($) | Dec. 31, 2018 USD ($) | Dec. 31, 2017 USD ($) | Dec. 31, 2016 USD ($) | Dec. 31, 2018 GBP (£) | Dec. 31, 2017 GBP (£) | Dec. 31, 2016 GBP (£) | Dec. 31, 2015 USD ($)
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net par amount of financial guarantees | $ 46,927,000 |  |  |  | $ 62,716,000 |  |  |  | $ 46,927,000 | $ 62,716,000 |  |  |  |  |
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest | 1,633,147 |  |  |  | $ 1,645,258 |  |  |  | 1,633,147 | $ 1,645,258 | $ 1,978,024 |  |  |  | $ 1,958,346
Stockholders Equity After Possible Increase in Domestic Public Finance Loss Reserves | 633,147 |  |  |  |  |  |  |  | 633,147 |  |  |  |  |  |
Possible Increase in Domestic Public Finance Loss Reserves | $ 1,000,000 |  |  |  |  |  |  |  | $ 1,000,000 |  |  |  |  |  |
Estimated Future Premium Payments Weighted Average Discounted Rate | 2.70% |  |  |  | 2.50% |  |  |  | 2.70% | 2.50% |  | 2.70% | 2.50% |  |
Ceded Loss And Loss Expenses Paid Not Yet Recovered | $ 510 |  |  |  | $ 339 |  |  |  | $ 510 | $ 339 | (349) |  |  |  |
Financial Guarantee Insurance Contracts, Premium Receivable | 495,391 |  |  |  | 586,312 |  |  |  | 495,391 | 586,312 | 661,337 |  |  |  | 831,575
Amount Of Insured Par Outstanding Ceded To Reinsurer | 3,076,000 |  |  |  |  |  |  |  | $ 3,076,000 |  |  |  |  |  |
Ceded Principal Outstanding Major Reinsurer Percentage |  |  |  |  |  |  |  |  | 5.90% |  |  |  |  |  |
Financial Guarantee Gross Outstanding Principal Assumed From Third Parties | 219,100 |  |  |  | 219,100 |  |  |  | $ 219,100 | 219,100 |  |  |  |  |
Deferred Ceded Premiums And Reinsurance Recoverables | 84,267 |  |  |  |  |  |  |  | 84,267 |  |  |  |  |  |
Reinsurance Payable | 32,913 |  |  |  | 37,876 |  |  |  | $ 32,913 | $ 37,876 |  |  |  |  |
Accrued rate of interest on outstanding policy obligations (percent) |  |  |  |  |  |  |  |  |  | 5.10% |  |  |  |  |
Weighted average period of future premiums |  |  |  |  |  |  |  |  | 8 years 8 months | 9 years 9 months 18 days |  |  |  |  |
Uncollectable premium receivables | 7,136 |  |  |  | 9,331 |  |  |  | $ 7,136 | $ 9,331 |  |  |  |  |
Accelerated premium revenue for retired obligations |  |  |  |  |  |  |  |  | 32,482 | 64,494 | 52,416 |  |  |  |
Reinsurance recoveries of losses included in losses and loss expenses |  |  |  |  |  |  |  |  | 1,657 | (20,348) | 5,421 |  |  |  |
Losses and loss expense reserves ceded to reinsurers | 22,623 |  |  |  | 40,658 |  |  |  | 22,623 | 40,658 | 30,767 |  |  |  | $ 44,059
Subrogation recoveries, net of reinsurance | (1,744,243) |  |  |  | (1,806,736) |  |  |  | (1,744,243) | (1,806,736) |  |  |  |  |
Intangible amortization expense | 28,982 | $ 26,421 | $ 23,242 | $ 28,636 | 34,168 | $ 45,690 | $ 33,471 | $ 37,525 | 107,281 | 150,854 | 174,608 |  |  |  |
Intangible Assets, Gross (Excluding Goodwill) | 1,551,576 |  |  |  | 1,581,156 |  |  |  | 1,551,576 | 1,581,156 |  |  |  |  |
Finite-Lived Intangible Assets, Accumulated Amortization | 832,645 |  |  |  | 734,183 |  |  |  | 832,645 | 734,183 |  |  |  |  |
Insurance intangible asset | 718,931 |  |  |  | 846,973 |  |  |  | 718,931 | 846,973 |  |  |  |  |
Letters of Credit Outstanding, Amount | 114,294 |  |  |  |  |  |  |  | 114,294 |  |  |  |  |  |
Financial Guarantee Outstanding Principal Ceded To Third Parties | 5,128,000 |  |  |  |  |  |  |  | 5,128,000 |  |  |  |  |  |
Premiums Past Due On Non Investment Grade Obligations | 100 |  |  |  |  |  |  |  | 100 |  |  |  |  |  |
Insurance Intangible Asset [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Intangible amortization expense |  |  |  |  |  |  |  |  | $ 107,281 | $ 150,854 | 174,608 |  |  |  |
Loss Reserves [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Weighted average risk-free rate used to discount loss reserves |  |  |  |  |  |  |  |  | 2.80% | 2.50% |  |  |  |  |
United Kingdom, Pounds |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Financial Guarantee Insurance Contracts, Premium Receivable | 131,458 |  |  |  | 151,852 |  |  |  | $ 131,458 | $ 151,852 | $ 177,878 | £ 103,088 | £ 112,342 | £ 144,393 |
Ambac UK [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Total Benefit Related to Ballantyne Settlement |  |  |  |  |  |  |  |  |  | 144,600 |  |  |  |  |
Commonwealth of Puerto Rico [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Domestic Public Finance Losses |  |  |  |  |  |  |  |  | 36,674 |  |  |  |  |  |
Public Finance [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net par amount of financial guarantees | 23,442,000 |  |  |  | 32,088,000 |  |  |  | 23,442,000 | 32,088,000 |  |  |  |  |
Housing Revenue [Member] | Public Finance [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net par amount of financial guarantees | 6,159,000 |  |  |  | 6,312,000 |  |  |  | 6,159,000 | 6,312,000 |  |  |  |  |
Housing Revenue [Member] | Military Housing [Domain] | Public Finance [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net par amount of financial guarantees | $ 5,759,000 |  |  |  | $ 5,829,000 |  |  |  | $ 5,759,000 | $ 5,829,000 |  |  |  |  |

X
- Definition Amount of insured par outstanding ceded to reinsurer. + References No definition available. + Details
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- Definition This element represents the reduction to gross claim liability for subrogation on insured RMBS financial obligations with credit deterioration, net of reinsurance. + References No definition available. + Details
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- Definition Ceded Loss And Loss Expenses Paid Not Yet Recovered + References No definition available. + Details
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- Definition Ceded Principal Outstanding Major Reinsurer Percentage. + References No definition available. + Details
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- Definition Reflects the effective interest rate on Deferred Amounts and Junior Deferred Amounts of the Segregated Account of Ambac as directed by the Rehabilitator of the Segregated Account. + References No definition available. + Details
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- Definition Includes the unexpired portion of financial guarantee premiums ceded on policies as of the balance sheet date and reinsurance recoverables on claims or claim adjustment expense paid by the ceding insurer. + References No definition available. + Details
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- Definition Domestic Public Finance Losses + References No definition available. + Details
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- Definition Weighted average discounted rate of estimated future premium payments to be paid by the VIEs. + References No definition available. + Details
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- Definition Financial Guarantee Gross Outstanding Principal Assumed from third parties. + References No definition available. + Details
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- Definition Financial Guarantee Outstanding Principal Ceded to third parties. + References No definition available. + Details
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- Definition Insurance [Line Items] + References No definition available. + Details
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- Definition The known and estimated amount recoverable as of the balance sheet date from reinsurers for claims expected to be paid or incurred by the ceding insurer. + References No definition available. + Details
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- Definition Possible Increase in Domestic Public Finance Loss Reserves + References No definition available. + Details
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- Definition Premiums Past Due On Non Investment Grade Obligations + References No definition available. + Details
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- Definition Stockholders Equity After Possible Increase in Domestic Public Finance Loss Reserves + References No definition available. + Details
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- Definition Total Benefit Related to Ballantyne Settlement + References No definition available. + Details
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- Definition The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3602-108585 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 50 -Paragraph 2 -Subparagraph (a)(2) -URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6388964&loc=d3e16225-109274 + Details
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- Definition This element represents the amount of premium revenue on financial guarantee insurance contracts recognized during the period that was accelerated for revenue recognition purposes. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 605 -Section 50 -Paragraph 4 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=6933581&loc=SL5749298-161291 + Details
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- Definition This element represents the weighted average risk free rate used to discount the claim liability related to financial guarantee insurance contracts. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 9 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=99382878&loc=SL5749324-161292 + Details
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- Definition Amount of the premium receivable for financial guarantee insurance contracts reported in the statement of financial position. This element primarily would consist of those financial guarantee insurance contracts which premiums are to be collected over the contract period, but may, on occasion, include premiums which are to be collected in full at inception, but which straddle a financial reporting period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 310 -Section 50 -Paragraph 3 -Subparagraph (c)(1),(5) -URI http://asc.fasb.org/extlink&oid=6933075&loc=SL5748726-161290 + Details
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- Definition Weighted average period over which premium receivable for financial guarantee insurance contracts is collected where premium is received over the contract period, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 310 -Section 50 -Paragraph 3 -Subparagraph (a)(5) -URI http://asc.fasb.org/extlink&oid=6933075&loc=SL5748726-161290 + Details
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- Definition Accumulated amount of amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 50 -Paragraph 2 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275 + Details
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- Definition Amount before accumulated amortization of intangible assets, excluding goodwill. + References No definition available. + Details
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- Definition Sum of the carrying amounts of all intangible assets, excluding goodwill, as of the balance sheet date, net of accumulated amortization and impairment charges. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 50 -Paragraph 2 -Subparagraph ((a)(1),(b)) -URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6388964&loc=d3e16212-109274 + Details
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- Definition The total amount of the contingent obligation under letters of credit outstanding as of the reporting date. + References No definition available. + Details
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- Definition Amount of participating insurance in force. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 50 -Section 50 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=6483535&loc=d3e16392-158451 + Details
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- Definition The carrying value as of the balance sheet date of the estimated valuation allowance to reduce gross premiums receivable to net realizable value. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953423-111524 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(5)) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5074-111524 + Details
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- Definition Amount of reduction of provision for policy benefits and costs incurred for policies ceded. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 20 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=99397103&loc=d3e6811-158387 + Details
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- Definition The carrying amount as of the balance sheet date of the known and estimated amounts owed to insurers under reinsurance treaties or other arrangements. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03.13(a)(3),(c)) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 + Details
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- Definition Amount of stockholders' equity (deficit), net of receivables from officers, directors, owners, and affiliates of the entity, attributable to both the parent and noncontrolling interests. Amount excludes temporary equity. Alternate caption for the concept is permanent equity. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 45 -Paragraph 16 -URI http://asc.fasb.org/extlink&oid=108774443&loc=SL4568740-111683 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 55 -Paragraph 4I -URI http://asc.fasb.org/extlink&oid=84234705&loc=SL4590271-111686 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 45 -Paragraph 15 -URI http://asc.fasb.org/extlink&oid=108774443&loc=SL4568447-111683 + Details
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