Members' Capital (Narrative) (Details) - shares	12 Months Ended
Members' Capital (Narrative) (Details) - shares	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Other Members Capital Account [Line Items]
Potential repurchase price of Units as percentage of holder's capital account	100.00%
Allocation of net income and net loss	100.00%
Other Members [Member]
Other Members Capital Account [Line Items]
Members capital account, Units issued	6,542,557	6,542,557
Members capital account, Units outstanding	6,542,557	6,542,557	6,542,557
Allocation of net income and net losses from commencement until initial closing date	92.50%
Percentage of fund distributions	92.50%
Managing Member [Member]
Other Members Capital Account [Line Items]
Members capital account, Units issued	50	50
Allocation of net income and net loss	99.00%
Allocation of net income and net losses from commencement until initial closing date	7.50%
Percentage of fund distributions	7.50%
Initial Member [Member]
Other Members Capital Account [Line Items]
Members capital account, Units issued	6,542,557
Members capital account, Units outstanding	6,542,557
Allocation of net income and net loss	1.00%
Maximum [Member] \| Managing Member [Member]
Other Members Capital Account [Line Items]
Members capital account, units authorized	15,000,000	15,000,000

ATEL 15, LLC 10-K