Fair Value Measurements (Estimated Fair Values of Financial Instruments) (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Dec. 31, 2017
Financial assets:
Warrants	$ 384		$ 561	$ 541
Level 1 Estimated Fair Value [Member]
Financial assets:
Investment in securities	56	$ 86	117	143	$ 176	$ 92
Level 3 Estimated Fair Value [Member]
Financial assets:
Warrants	384	$ 386	561	$ 541	$ 542	$ 489
Carrying Amount [Member]
Financial assets:
Cash and cash equivalents	333		214
Notes receivable, net	719		2,188
Investment in securities	56		117
Warrants	384		561
Estimate of Fair Value [Member]
Financial assets:
Cash and cash equivalents	333		214
Notes receivable, net	746		2,266
Investment in securities	56		117
Warrants	384		561
Estimate of Fair Value [Member] \| Level 1 Estimated Fair Value [Member]
Financial assets:
Cash and cash equivalents	333		214
Investment in securities	56		117
Estimate of Fair Value [Member] \| Level 2 Estimated Fair Value [Member]
Financial assets:
Cash and cash equivalents
Notes receivable, net
Investment in securities
Warrants
Estimate of Fair Value [Member] \| Level 3 Estimated Fair Value [Member]
Financial assets:
Notes receivable, net	746		2,266
Warrants	$ 384		$ 561

ATEL Growth Capital Fund 8, LLC 10-Q