Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2017	Feb. 28, 2018
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	FY
Trading Symbol	CK0000889123
Entity Registrant Name	REDWOOD MORTGAGE INVESTORS VIII
Entity Central Index Key	0000889123
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Smaller Reporting Company
Entity Common Stock, Shares Outstanding		147,329,043
Entity Public Float	$ 0