XML 111 R91.htm IDEA: XBRL DOCUMENT
v3.10.0.1

Investments - Summary of Fair Value, Including Financial Guarantee, and Weighted-Average Underlying Rating, Excluding Financial Guarantee, of Insured Securities (Detail2) - USD ($) $ in Thousands | Dec. 31, 2018 | Dec. 31, 2017
--- | --- | ---
Ambac UK [Member] |  |
Investment [Line Items] |  |
Asset-backed securities fair value | $ 144,672 | $ 170,280

X
- Definition Asset-backed securities guaranteed by Ambac UK. + References No definition available. + Details
Name: | ambc_AssetBackedSecuritiesFairValueDisclosure
Namespace Prefix: | ambc_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Line items represent reporting 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 Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Article 12 -Section 12 -Sentence Column A + Details
Name: | invest_InvestmentLineItems
Namespace Prefix: | invest_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | dei_LegalEntityAxis=ambc_AmbacUkMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |