Allowance for Credit Losses (Net Investment in Financing Receivables by Age) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due
Current	3,164	$ 3,054
Total financing receivables	3,164	3,054
Recorded Investment > 90 Days and Accruing
Financing Receivables 31-60 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due
Financing Receivables 61-90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due
Greater Than 90 Days [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due
Notes Receivable [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due
Current	3,164	3,054
Total financing receivables	3,164	3,054
Recorded Investment > 90 Days and Accruing
Notes Receivable [Member] \| Financing Receivables 31-60 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due
Notes Receivable [Member] \| Financing Receivables 61-90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due
Notes Receivable [Member] \| Greater Than 90 Days [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due

ATEL Growth Capital Fund 8, LLC 10-Q