Document and Entity Information - USD ($) $ in Thousands, shares in Millions	12 Months Ended
	Dec. 31, 2022	Feb. 28, 2023
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2022
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	FY
No Trading Symbol Flag	true
Title of 12(g) Security	Limited Partnership Interests
Entity Registrant Name	REDWOOD MORTGAGE INVESTORS VIII, L.P.
Entity Central Index Key	0000889123
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Common Stock, Shares Outstanding		57.5
Entity Current Reporting Status	Yes
ICFR Auditor Attestation Flag	false
Entity Interactive Data Current	Yes
Entity Voluntary Filers	No
well-known seasoned issuer	No
Entity Shell Company	false
Document Annual Report	true
Document Transition Report	false
Entity File Number	000-27816
Entity Incorporation, State or Country Code	CA
Entity Tax Identification Number	94-3158788
Entity Address, Address Line One	177 Bovet Road
Entity Address, Address Line Two	Suite 520
Entity Address, City or Town	San Mateo
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94402
City Area Code	650
Local Phone Number	365-5341
Entity Public Float	$ 0
Auditor Firm ID	243
Auditor Name	BDO USA, LLP
Auditor Location	San Francisco, California