Revenue from Contract with Customer Revenue, Remaining Performance Obligation (Details) $ in Millions	Sep. 30, 2018 USD ($)
Revenue, Remaining Performance Obligation [Abstract]
Revenue, Remaining Performance Obligation, Amount	$ 963.2
Revenue, Remaining Performance Obligation, Current	184.2
Revenue, Remaining Performance Obligation, Noncurrent	$ 779.0

Amount of transaction price allocated to performance obligation that has not been recognized as revenue and is expected to be recognized as revenue beyond the next year.

No definition available.

Name:	arii_RevenueRemainingPerformanceObligationNoncurrent
Namespace Prefix:	arii_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant