Commitments and Contingent Liabilities (Details) $ in Thousands	Mar. 31, 2016 USD ($)
Commitments and Contingencies Disclosure [Abstract]
Irrevocable letters of credit outstanding	$ 8,738
Letters of Credit Outstanding as Collateral for Janesville lease	5,000
Letters of credit outstanding for insurance reserve requirements of workers' compensation insurance carriers	$ 1,538

The amount of letters of credit outstanding which are required to be in compliance with workers' compensation insurance carriers reserve requirements.

No definition available.

Name:	cas_LettersOfCreditOutstandingForWorkersCompensationInsuranceReserve
Namespace Prefix:	cas_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant