Manager and Other Related Parties - Additional Information (Details) $ in Thousands	1 Months Ended		3 Months Ended		9 Months Ended
	May 31, 2024 USD ($)	Jun. 30, 2023 USD ($) Loan	Sep. 30, 2024 USD ($)	Sep. 30, 2023 USD ($)	Sep. 30, 2024 USD ($) Loan	Sep. 30, 2023 USD ($) Loan	Aug. 31, 2024 USD ($)	Jun. 30, 2024 USD ($)	Dec. 31, 2023 USD ($)	Apr. 30, 2019 USD ($)
Managers And Other Related Parties Details [Line Items]
Managers Share of net income or loss					1.00%
Total members capital account redemptions unpaid					$ 20,800
Principal Amount Of Loans Transferred From Related Mortgage Funds				$ 3,400		$ 3,400
Principal Amount of Loans Transferred to Related Mortgage Funds						1,100
Number Of Mortgage Loans As Security To Pay The Promissory Note \| Loan		3
Redemptions on death, Cap			$ 100		100
Promissory note funded to related mortgage fund					$ 0	$ 3,300
Number Of Loans Transferred From Related Mortgage Funds \| Loan					0	4
Number of loans transferred to related mortgage funds \| Loan					0	3
Unpaid Total Members Capital Account Redemptions			4,200		$ 4,200			$ 16,600
Original formation loan										$ 5,600
Reimbursement as a percentage of member's original purchase price					0.45%
Percentage of original purchase price, quarterly installment percentage					0.1125%
Mortgage Loans amount			1,307		$ 36,501
Accounts Payable And Cost Reimbursements [Member]
Managers And Other Related Parties Details [Line Items]
Payable Related parties			44		44				$ 57
Accounts Payable Related to Mortgage Fund [Member]
Managers And Other Related Parties Details [Line Items]
Payable Related parties									18
Accounts Payable And Cost Member Redemptions [Member]
Managers And Other Related Parties Details [Line Items]
Payable Related parties									15
Redwood Mortgage Investors VIII [Member]
Managers And Other Related Parties Details [Line Items]
Promissory note funded to related mortgage fund		$ 3,300
Net Cash Flow From Collateral Mortgage Loans		$ 7,500
Borrowing from related mortgage funds	$ 940							$ 2,500
Borrowings from the manager							$ 50
Mortgage loan principal amount	$ 9,100
RMC [Member]
Managers And Other Related Parties Details [Line Items]
Total amount of loan administrative fees waived			$ 13	56	$ 365	$ 236
Management Fee, Percentage			0.75%		0.75%
Working Capital Reserve, Percentage			2.00%		2.00%
Qualifying costs incurred			$ 131	188	$ 402	606
Reimbursement of costs from RMC waived			$ 53	$ 90	$ 162	$ 339
Administrative Fees, Percentage			1.00%		1.00%
Maximum Advance As A Percentage of Offering Proceeds					7.00%
Repayment of formation loan in annual installments			$ 208		$ 208
RMC [Member] \| Accounts Payable And Cost Reimbursements [Member]
Managers And Other Related Parties Details [Line Items]
Payable Related parties			$ 44		$ 44				$ 90
Maximum [Member]
Managers And Other Related Parties Details [Line Items]
Percentage of reimbursement of organization and offering expenses					4.50%
Reimbursement threshold					for each of forty (40) calendar quarters or portion thereof after December 31, 2015
Maximum [Member] \| RMC [Member]
Managers And Other Related Parties Details [Line Items]
Annual mortgage servicing fees, percentage			0.25%		0.25%

Redwood Mortgage Investors IX 10-Q