Loans - Secured Loans Characteristics (Details) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2021 USD ($) County Loan	Dec. 31, 2020 USD ($) Loan County	Jun. 30, 2021 USD ($)
Secured Loan Transactions [Line Items]
Number of secured loans | Loan	33	33
Secured loans - principal (in Dollars)	$ 70,227	$ 74,080	$ 72,548
Average secured loan - principal (in Dollars)	$ 2,128	$ 2,245
Average principal as percent of total principal	3.00%	3.00%
Average principal as percent of partners’ capital, net of formation loan	3.10%	2.90%
Average principal as percent of total assets	2.60%	2.70%
Largest secured loan - principal (in Dollars)	$ 10,200	$ 10,200
Largest principal as percent of total principal	14.50%	13.80%
Largest principal as percent of partners’ capital, net of formation loan	14.90%	13.00%
Largest principal as percent of total assets	12.60%	12.10%
Smallest secured loan - principal (in Dollars)	$ 57	$ 46
Smallest principal as percent of total principal	0.10%	0.10%
Smallest principal as percent of partners’ capital, net of formation loan	0.10%	0.10%
Smallest principal as percent of total assets	0.10%	0.10%
Number of California counties where security is located | County	12	14
Largest percentage of principal in one California county	38.60%	40.00%
Minimum [Member]
Secured Loan Transactions [Line Items]
Secured loans - interest rate (fixed)	7.00%	5.00%
Maximum [Member]
Secured Loan Transactions [Line Items]
Secured loans - interest rate (fixed)	10.80%	10.80%