Name:	cas_EarningsBeforeInterestTaxesDepreciationAndAmortizationToFixedChargesRatio
Namespace Prefix:	cas_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

The lower bound of excess revolver availability as defined in Revolving Credit Facility Agreement, under which amount the Company must retain a ratio of EBITDA to fixed charges of 1.1 to 1.0.

No definition available.

Name:	cas_ExcessAvailabilitylowerboundfixedchargecoverage
Namespace Prefix:	cas_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

The lower bound of excess revolver availability under which amount the lender has the right to take full dominion of the Company's cash collections and apply them to outstanding loans under the Revolving Credit Agreement.

No definition available.

Name:	cas_ExcessAvailabilitylowerboundlenderfulldominionovercollections
Namespace Prefix:	cas_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Lower bound percentage of excess availability to calculated borrowing base, under which percentage the Company must maintain a ratio of EBITDA to fixed charges of 1.1 to 1.0.

No definition available.

Name:	cas_Excessavailabilitypercentageofborrowingbaselowerboundfixedchargecoverage
Namespace Prefix:	cas_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

The lower bound excess availability percentage of borrowing base where the lender has the right to take full dominion of the Company's cash collections and apply them to amounts outstanding under the Revolving Credit Facility.

No definition available.

Name:	cas_Excessavailabilitypercentageofborrowingbaselowerboundlenderfulldominionovercollections
Namespace Prefix:	cas_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Line of Credit, Terms, Provision to Increase the Aggregate Amount of Commitments Under Certain Conditions, Amount

No definition available.

Name:	cas_LineOfCreditTermsProvisionToIncreaseAggregateAmountOfCommitmentsUnderCertainConditionsAmount
Namespace Prefix:	cas_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

The amount the availability block which decreases availability under the Company's revolving credit facility is reduced to if the Company's ratio of EBITDA to fixed charges (as defined by the Revolving Credit Facility Loan and Security Agreement) is at least 1.0 to 1.0 for each of the proceeding 6 months.

No definition available.

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

The amount the availability block which decreases the availability under the Company's revolving credit facility is reduced to if the Company's ratio of EBITDA to fixed charges (as defined in the Revolving Credit Facility Loan and Security Agreement) is a least 1.0 to 1.0 for any of the previous trailing 12 month period.

No definition available.

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

The initial amount of the availability block which restricts the availability of borrowings under the Company's revolving credit agreement, as amended.

No definition available.

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

Line of Credit Facility, Borrowing Capacity excluding minimum excess availability, springing covenant

No definition available.

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

Pursuant to the terms of the June 2016 Amendment to the Company's Revolving Credit Agreement, the maximum amount of the New Senior Secured Notes due December 2018 that the Company is permitted to repay subject to the satisfaction of revised financial testing conditions.

No definition available.

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

Pursuant to the terms of the June 2016 Amendment to the Company's Revolving Credit Agreement, the maximum amount of the existing Senior Secured Notes due December 2016 that the Company is permitted to repay subject to the satisfaction of revised financial testing conditions.

No definition available.

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

The average effective interest rate during the reporting period.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28551-108399

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Name:	us-gaap_DebtInstrumentInterestRateDuringPeriod
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

Name:	us-gaap_DebtInstrumentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(2))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Name:	us-gaap_DebtInstrumentMaturityDate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Name:	us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Name:	us-gaap_DebtInstrumentAxis=us-gaap_RevolvingCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_StatementGeographicalAxis=country_CA
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: