ORGANIZATION AND OPERATIONS OF THE FUND (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	6 Months Ended
	Jul. 31, 2015	Jun. 30, 2023	Dec. 31, 2022
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Common stock, par value (in dollars per share)		$ 0.001	$ 0.001
Investment Company, Regulated Status [true false]		true
Venture Lending & Leasing VIII, Inc.
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Number of shares issued in sale (in shares)	100,000
Common stock, par value (in dollars per share)	$ 0.001
Proceeds from purchase of shares	$ 25
Venture Lending & Leasing VIII, Inc. | Venture Lending & Leasing VIII, LLC
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Ownership percentage		100.00%