Loans - Secured Loans Characteristics (Details)	3 Months Ended	12 Months Ended
	Mar. 31, 2018 USD ($) MortgageLoan Country	Dec. 31, 2017 USD ($) MortgageLoan Country
Secured Loan Transactions [Line Items]
Number of secured loans | MortgageLoan	93	93
Secured loans - principal (in Dollars)	$ 57,865,391	$ 54,768,689
Average secured loan - principal (in Dollars)	$ 622,209	$ 588,911
Average principal as percent of total principal	1.10%	1.10%
Average principal as percent of members’ capital	0.90%	0.90%
Average principal as percent of total assets	0.90%	0.90%
Largest secured loan - principal (in Dollars)	$ 3,200,000	$ 3,239,124
Largest principal as percent of total principal	5.50%	5.90%
Largest principal as percent of members’ capital	4.70%	5.00%
Largest principal as percent of total assets	4.70%	5.10%
Smallest secured loan - principal (in Dollars)	$ 94,425	$ 52,562
Smallest principal as percent of total principal	0.20%	0.10%
Smallest principal as percent of members’ capital	0.10%	0.10%
Smallest principal as percent of total assets	0.10%	0.10%
Number of California counties where security is located | Country	17	16
Largest percentage of principal in one California county	18.80%	22.60%
Secured loans in foreclosure - principal (in Dollars)	$ 139,162	$ 139,643
Minimum [Member]
Secured Loan Transactions [Line Items]
Secured loans – interest rate (fixed)	6.90%	6.90%
Maximum [Member]
Secured Loan Transactions [Line Items]
Secured loans – interest rate (fixed)	10.50%	10.50%
Filed Notice of Default [Member]
Secured Loan Transactions [Line Items]
Number of secured loans | MortgageLoan	1	1