Fair Value Measurements (Estimated Fair Values of Financial Instruments) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Financial assets:
Cash and cash equivalents	$ 6,410	$ 6,484
Notes receivable, net	1,086	3,370
Warrants, fair value	731	302
Financial liabilities:
Non-recourse debt	3,516	3,539
Carrying Amount [Member]
Financial assets:
Cash and cash equivalents	6,410	6,484
Notes receivable, net	1,078	3,455
Warrants, fair value	731	302
Financial liabilities:
Non-recourse debt	3,508	3,531
Fair Value, Inputs, Level 1 [Member]
Financial assets:
Cash and cash equivalents	6,410	6,484
Fair Value, Inputs, Level 3 [Member]
Financial assets:
Notes receivable, net	1,086	3,370
Warrants, fair value	731	302	$ 62
Financial liabilities:
Non-recourse debt	$ 3,516	$ 3,539