Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2020	Mar. 03, 2021	Jun. 30, 2020
Document and Entity Information
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Entity Registrant Name	RIDGEFIELD ACQUISITION CORP
Entity Central Index Key	0000812152
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Trading Symbol	RDGA
Title of 12(g) Security	Common Stock, $0.001 par value
Entity Common Stock, Shares Outstanding		1,260,773
Entity Shell Company	true
Entity Emerging Growth Company	false
Entity Small Business	true
Entity Voluntary Filers	No
Entity Well-known Seasoned Issuer	No
Entity Public Float			$ 371,028
ICFR Auditor Attestation Flag	false