XML 20 R1.htm IDEA: XBRL DOCUMENT v3.19.1
Document and Entity Information - $ / shares
 3 Months Ended
Mar. 31, 2019
May 06, 2019
Dec. 31, 2018
Apr. 30, 2013
Entity Information [Line Items]        
Entity Incorporation, State Country Name Delaware      
Entity Tax Identification Number 133621676      
Local Phone Number 212-658-7470      
Entity Address, Address Line One One State Street Plaza      
Entity Address, City or Town New York      
Entity Address, State or Province NY      
Entity Address, Postal Zip Code 10004      
Common Stock, Par or Stated Value Per Share $ 0.01   $ 0.01 $ 0.01
Document Type 10-Q      
Amendment Flag false      
Document Period End Date Mar. 31, 2019      
Document Fiscal Year Focus 2019      
Document Fiscal Period Focus Q1      
Trading Symbol AMBC      
Entity Registrant Name AMBAC FINANCIAL GROUP INC      
Entity Central Index Key 0000874501      
Current Fiscal Year End Date --12-31      
Entity Current Reporting Status Yes      
Entity Filer Category Large Accelerated Filer      
Entity Small Business false      
Entity Emerging Growth Company false      
Entity Common Stock, Shares Outstanding   45,520,541