Document And Entity Information (USD $)	3 Months Ended
	Mar. 31, 2012
Entity Registrant Name	AMBASE CORP
Entity Central Index Key	0000020639
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	No
Entity Filer Category	Smaller Reporting Company
Entity Public Float	$ 70,230,326
Entity Common Stock, Shares Outstanding	43,075,410
Document Fiscal Year Focus	2012
Document Fiscal Period Focus	Q1
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2012