Loans - Secured Loans Distributed within California (Details) - USD ($) $ in Thousands		Sep. 30, 2021	Jun. 30, 2021	Dec. 31, 2020
Loans (Details) - Secured Loans by Property Type [Line Items]
Secured loans, principal		$ 70,227	$ 72,548	$ 74,080
Loans - percent		100.00%		100.00%
San Francisco [Member]
Loans (Details) - Secured Loans by Property Type [Line Items]
Secured loans, principal	[1]	$ 27,121		$ 29,659
Loans - percent	[1]	38.60%		40.00%
San Mateo [Member]
Loans (Details) - Secured Loans by Property Type [Line Items]
Secured loans, principal		$ 8,610		$ 16,756
Loans - percent		12.30%		22.60%
Alameda [Member]
Loans (Details) - Secured Loans by Property Type [Line Items]
Secured loans, principal		$ 6,240		$ 823
Loans - percent		8.90%		1.10%
Santa Clara [Member]
Loans (Details) - Secured Loans by Property Type [Line Items]
Secured loans, principal		$ 4,600		$ 4,600
Loans - percent		6.60%		6.20%
Marin [Member]
Loans (Details) - Secured Loans by Property Type [Line Items]
Secured loans, principal		$ 1,656		$ 917
Loans - percent		2.30%		1.20%
Sonoma [Member]
Loans (Details) - Secured Loans by Property Type [Line Items]
Secured loans, principal		$ 578
Loans - percent		0.80%		0.00%
Contra Costa [Member]
Loans (Details) - Secured Loans by Property Type [Line Items]
Secured loans, principal				$ 302
Loans - percent				0.40%
San Francisco Bay Area [Member]
Loans (Details) - Secured Loans by Property Type [Line Items]
Secured loans, principal		$ 48,805		$ 53,057
Loans - percent		69.50%		71.50%
Mariposa [Member]
Loans (Details) - Secured Loans by Property Type [Line Items]
Secured loans, principal		$ 57		$ 46
Loans - percent		0.10%		0.10%
Placer [Member]
Loans (Details) - Secured Loans by Property Type [Line Items]
Secured loans, principal				$ 1,500
Loans - percent		0.00%		2.00%
Santa Cruz [Member]
Loans (Details) - Secured Loans by Property Type [Line Items]
Secured loans, principal				$ 485
Loans - percent		0.00%		0.70%
Amador [Member]
Loans (Details) - Secured Loans by Property Type [Line Items]
Secured loans, principal				$ 701
Loans - percent		0.00%		0.90%
Other Northern California [Member]
Loans (Details) - Secured Loans by Property Type [Line Items]
Secured loans, principal		$ 57		$ 2,732
Loans - percent		0.10%		3.70%
Northern California [Member]
Loans (Details) - Secured Loans by Property Type [Line Items]
Secured loans, principal		$ 48,862		$ 55,789
Loans - percent		69.60%		75.20%
Los Angeles [Member]
Loans (Details) - Secured Loans by Property Type [Line Items]
Secured loans, principal		$ 11,269		$ 10,199
Loans - percent		16.00%		13.80%
Orange [Member]
Loans (Details) - Secured Loans by Property Type [Line Items]
Secured loans, principal		$ 2,194		$ 642
Loans - percent		3.10%		0.90%
Santa Barbara [Member]
Loans (Details) - Secured Loans by Property Type [Line Items]
Secured loans, principal		$ 2,062		$ 2,070
Loans - percent		2.90%		2.80%
Riverside [Member]
Loans (Details) - Secured Loans by Property Type [Line Items]
Secured loans, principal		$ 460
Loans - percent		0.70%		0.00%
Los Angeles And Coastal [Member]
Loans (Details) - Secured Loans by Property Type [Line Items]
Secured loans, principal		$ 15,985		$ 12,911
Loans - percent		22.70%		17.50%
San Bernardino [Member]
Loans (Details) - Secured Loans by Property Type [Line Items]
Secured loans, principal		$ 5,380		$ 5,380
Loans - percent		7.70%		7.30%
Other Southern California [Member]
Loans (Details) - Secured Loans by Property Type [Line Items]
Secured loans, principal		$ 5,380		$ 5,380
Loans - percent		7.70%		7.30%
Southern California [Member]
Loans (Details) - Secured Loans by Property Type [Line Items]
Secured loans, principal		$ 21,365		$ 18,291
Loans - percent		30.40%		24.80%

[1] Includes the Silicon Valley