XML 81 R63.htm IDEA: XBRL DOCUMENT
v3.21.1

Investments - Summary of Amortized Cost and Estimated Fair Value of Available-for-Sale Investments, Excluding VIE Investments (Details) - USD ($) $ in Millions | Mar. 31, 2021 | Dec. 31, 2020
--- | --- | ---
Debt Securities, Available-for-sale [Line Items] |  |
Debt Securities, Available-for-sale, Unrealized Loss Position | $ 669 | $ 841
Debt Securities, Available-for-sale, Amortized Cost | 2,739 | 2,807
Debt Securities, Available-for-sale, Allowance for Credit Loss | 0 | 0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 136 | 149
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months | 638 | 816
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | 17 | 7
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer | 31 | 25
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | 0 | 0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 17 | 8
Available-for-sale Securities, Current | 2,858 | 2,949
Fixed maturity securities, at fair value | 2,858 |
Short-term Investments [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Debt Securities, Available-for-sale, Unrealized Loss Position | 157 | 187
Debt Securities, Available-for-sale, Amortized Cost | 398 | 492
Debt Securities, Available-for-sale, Allowance for Credit Loss | 0 | 0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 0 | 0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months | 157 | 187
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | 0 | 0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer | 0 | 0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | 0 | 0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 0 | 0
Fixed maturity securities, at fair value | 397 | 492
Fixed Income Securities [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Debt Securities, Available-for-sale, Unrealized Loss Position | 512 | 654
Debt Securities, Available-for-sale, Amortized Cost | 2,221 | 2,175
Debt Securities, Available-for-sale, Allowance for Credit Loss | 0 | 0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 136 | 149
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months | 481 | 629
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | 17 | 7
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer | 31 | 25
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | 0 | 0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 17 | 8
Fixed maturity securities, at fair value | 2,341 | 2,317
Fixed Income Securities [Member] | Municipal Bonds [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Debt Securities, Available-for-sale, Unrealized Loss Position | 35 | 31
Debt Securities, Available-for-sale, Amortized Cost | 329 | 321
Debt Securities, Available-for-sale, Allowance for Credit Loss | 0 | 0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 38 | 37
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months | 19 | 25
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | 0 | 0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer | 16 | 6
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | 0 | 0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 0 | 0
Fixed maturity securities, at fair value | 366 | 358
Fixed Income Securities [Member] | Corporate Debt Securities [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Debt Securities, Available-for-sale, Unrealized Loss Position | 339 | 543
Debt Securities, Available-for-sale, Amortized Cost | 1,106 | 1,059
Debt Securities, Available-for-sale, Allowance for Credit Loss | 0 | 0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 14 | 24
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months | 339 | 543
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | 13 | 6
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer | 0 | 0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | 0 | 0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 13 | 6
Fixed maturity securities, at fair value | 1,108 | 1,077
Fixed Income Securities [Member] | Foreign Obligations [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Debt Securities, Available-for-sale, Unrealized Loss Position | 70 | 3
Debt Securities, Available-for-sale, Amortized Cost | 98 | 97
Debt Securities, Available-for-sale, Allowance for Credit Loss | 0 | 0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 0 | 1
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months | 70 | 3
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | 1 | 0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer | 0 | 0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | 0 | 0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 1 | 0
Fixed maturity securities, at fair value | 97 | 98
Fixed Income Securities [Member] | US Government Debt Securities [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Debt Securities, Available-for-sale, Unrealized Loss Position | 25 | 17
Debt Securities, Available-for-sale, Amortized Cost | 109 | 105
Debt Securities, Available-for-sale, Allowance for Credit Loss | 0 | 0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 1 | 2
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months | 25 | 17
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | 2 | 1
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer | 0 | 0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | 0 | 0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 2 | 1
Fixed maturity securities, at fair value | 108 | 106
Fixed Income Securities [Member] | Residential Mortgage-Backed Securities [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Debt Securities, Available-for-sale, Unrealized Loss Position | 17 | 14
Debt Securities, Available-for-sale, Amortized Cost | 219 | 256
Debt Securities, Available-for-sale, Allowance for Credit Loss | 0 | 0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 50 | 46
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months | 15 | 14
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | 0 | 0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer | 2 | 0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | 0 | 0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 0 | 0
Fixed maturity securities, at fair value | 269 | 302
Fixed Income Securities [Member] | Collateralized Debt Obligations [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Debt Securities, Available-for-sale, Unrealized Loss Position | 26 | 42
Debt Securities, Available-for-sale, Amortized Cost | 97 | 74
Debt Securities, Available-for-sale, Allowance for Credit Loss | 0 | 0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 0 | 0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months | 13 | 27
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | 0 | 0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer | 13 | 15
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | 0 | 0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 0 | 0
Fixed maturity securities, at fair value | 97 | 74
Fixed Income Securities [Member] | Asset-backed Securities [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Debt Securities, Available-for-sale, Unrealized Loss Position | 0 | 4
Debt Securities, Available-for-sale, Amortized Cost | 262 | 263
Debt Securities, Available-for-sale, Allowance for Credit Loss | 0 | 0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 33 | 40
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months | 0 | 0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | 0 | 0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer | 0 | 4
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | 0 | 0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 0 | 0
Fixed maturity securities, at fair value | 295 | 303
Fixed Income Investments And Other Investments [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Debt Securities, Available-for-sale, Amortized Cost | 2,619 | 2,667
Debt Securities, Available-for-sale, Allowance for Credit Loss | 0 | 0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 136 | 149
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 17 | 8
Fixed maturity securities, at fair value | 2,738 | 2,809
Collateral Pledged [Member] | Fixed Income Securities [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 0 | 0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 0 | 0
Fixed maturity securities, at fair value | 120 | 140
Collateral Pledged [Member] | Fixed Income Securities [Member] | Short-term Investments [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Debt Securities, Available-for-sale, Amortized Cost | 105 | 125
Debt Securities, Available-for-sale, Allowance for Credit Loss | 0 | 0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 0 | 0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 0 | 0
Fixed maturity securities, at fair value | 105 | 125
Collateral Pledged [Member] | Fixed Income Securities [Member] | US Treasury and Government |  |
Debt Securities, Available-for-sale [Line Items] |  |
Debt Securities, Available-for-sale, Amortized Cost | 15 | 15
Debt Securities, Available-for-sale, Allowance for Credit Loss | 0 | 0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 0 | 0
Fixed maturity securities, at fair value | 15 | 15
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax | 0 | 0
Asset Pledged as Collateral [Member] | Fixed Income Securities [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Debt Securities, Available-for-sale, Amortized Cost | 120 | 140
Debt Securities, Available-for-sale, Allowance for Credit Loss | $ 0 | $ 0

X
- Definition Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563 + Details
Name: | us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563 + Details
Name: | us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale. + References No definition available. + Details
Name: | us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any. + References No definition available. + Details
Name: | us-gaap_AvailableForSaleSecuritiesAmortizedCost
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of investment in debt and equity securities categorized neither as trading securities nor held-to-maturity securities and intended be sold or mature one year or operating cycle, if longer. + References No definition available. + Details
Name: | us-gaap_AvailableForSaleSecuritiesCurrent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=118942338&loc=SL82898722-210454 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=118954083&loc=d3e26610-111562 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (aa) -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563 + Details
Name: | us-gaap_AvailableForSaleSecuritiesDebtSecurities
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of allowance for credit loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 50 -Paragraph 9 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=118955579&loc=SL82922900-210455 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 50 -Paragraph 9 -Subparagraph (i) -URI http://asc.fasb.org/extlink&oid=118955579&loc=SL82922900-210455 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (aaa) -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=118942338&loc=SL82898722-210454 + Details
Name: | us-gaap_DebtSecuritiesAvailableForSaleAllowanceForCreditLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=118955579&loc=SL82922890-210455 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27337-111563 Reference 3: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 55 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=118942371&loc=SL82922954-210456 + Details
Name: | us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of accumulated unrealized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for 12 months or longer, without allowance for credit loss. Includes beneficial interest in securitized financial asset. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27337-111563 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=118955579&loc=SL82922890-210455 + Details
Name: | us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for less than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27337-111563 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=118955579&loc=SL82922890-210455 Reference 3: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 55 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=118942371&loc=SL82922954-210456 + Details
Name: | us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of accumulated unrealized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for less than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=118955579&loc=SL82922890-210455 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27337-111563 + Details
Name: | us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in unrealized loss position without allowance for credit loss. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 6 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27290-111563 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 50 -Paragraph 4 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=118955579&loc=SL82922888-210455 Reference 3: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 55 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=118942371&loc=SL82922954-210456 + Details
Name: | us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPosition
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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
Name: | us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_ShortTermInvestmentsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=us-gaap_FixedIncomeSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_MunicipalBondsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_CorporateDebtSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_ForeignGovernmentDebtSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_USGovernmentDebtSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_ResidentialMortgageBackedSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_CollateralizedDebtObligationsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_AssetBackedSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=ambc_FixedIncomeInvestmentsAndOtherInvestmentsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_CollateralAxis=us-gaap_CollateralPledgedMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_USTreasuryAndGovernmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_CollateralAxis=us-gaap_AssetPledgedAsCollateralMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |