Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2018	Mar. 28, 2019	Jun. 30, 2018
Document and Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	FY
Entity Registrant Name	RIDGEFIELD ACQUISITION CORP
Entity Central Index Key	0000812152
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Non-accelerated Filer
Entity Public Float			$ 222,617
Trading Symbol	RDGA
Entity Common Stock, Shares Outstanding		1,260,773
Entity Shell Company	true
Entity Emerging Growth Company	false
Entity Small Business	true