Subsequent Events Tier 2 Financing (Details) - Subsequent Event [Member] $ in Thousands	Feb. 12, 2018 USD ($)
Tier 2 Notes	$ 240,000
Tier 2 Note Security in RMBS Litigation Settlement Proceeds	$ 1,600,000

Tier 2 Note Security in RMBS Litigation Settlement Proceeds

No definition available.

Name:	ambc_Tier2NoteSecurityinRMBSLitigationSettlementProceeds
Namespace Prefix:	ambc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant