Letter of Credit, Maximum

No definition available.

Name:	cmt_LetterofCreditMaximum
Namespace Prefix:	cmt_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Percent of Subsidiary Stock Not Security for Financing

+ References

No definition available.

+ Details

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Namespace Prefix:	cmt_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Purchase Price Funded with Debt - Amount of the purchase price of a business acquisition funded with debt

+ References

No definition available.

+ Details

Name:	cmt_PurchasePriceFundedwithDebt
Namespace Prefix:	cmt_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of short-term debt and current maturity of long-term debt and capital lease obligations due within one year or the normal operating cycle, if longer.

+ References

+ Details

Name:	us-gaap_DebtCurrent
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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)(1)
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-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

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

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
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+ Details

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

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

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.

+ References

No definition available.

+ Details

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Description of covenants that limit or prohibit certain actions or activities without the lender's prior consent within a specified period of time or until certain specified targets are achieved for example, reduction of the debt or an increase in net worth to a specified amount).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(e))
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+ Details

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

- Definition

Fixed interest rate related to the interest rate derivative.

+ References

No definition available.

+ Details

Name:	us-gaap_DerivativeFixedInterestRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Fair value portion of liability contracts related to the exchange of different currencies, including, but not limited to, foreign currency options, forward (delivery or nondelivery) contracts, and swaps entered into.

+ References

No definition available.

+ Details

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

- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

No definition available.

+ Details

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

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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+ Details

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

- Definition

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.

+ References

+ Details

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

- Definition

Including the current and noncurrent portions, aggregate carrying value as of the balance sheet date of loans payable (with maturities initially due after one year or beyond the operating cycle if longer).

+ References

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+ Details

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

- Definition

Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 4
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+ Details

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

- Definition

Amount after unamortized (discount) premium and debt issuance costs of long-term debt classified as noncurrent and excluding amounts to be repaid within one year or the normal operating cycle, if longer. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

+ Details

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

- Definition

Amount of deferred fees paid by borrowers and unamortized costs incurred to originate loans and leases, unamortized loan commitments and loan syndication fees, and premiums over or discounts from face amounts of loans that are being amortized into income as an adjustment to yield. Excludes amounts for loans and leases covered under loss sharing agreements.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 20
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6378536&loc=d3e10092-111533

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

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Namespace Prefix:
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Balance Type:
Period Type:

- Details

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Balance Type:
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- Details

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Balance Type:
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- Details

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Balance Type:
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- Details

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Balance Type:
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- Details

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- Details

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Debt (Details) - USD ($)	6 Months Ended	12 Months Ended
Debt (Details) - USD ($)	Jun. 30, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Debt	$ 60,041,000		$ 59,000,000
Loans Payable	39,938,000		41,625,000
Unamortized Loan Commitment and Origination Fees and Unamortized Discounts or Premiums	(941,000)		(611,000)
Revolving Line of Credit	20,103,000		17,375,000
Purchase Price Funded with Debt	49,500,000
Less current portion	(3,669,000)		(3,230,000)
Long-term Debt, Gross	55,431,000		55,159,000
Long-term debt	$ 35,328,000		37,784,000
Derivative, Fixed Interest Rate	2.49%
Percent of subsidiary stock not security for financing	65.00%
Letter of Credit, Maximum			250,000
Letters of Credit Outstanding, Amount			$ 160,000
Term Loan Domestic [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 32,000,000
Domestic Line of Credit [Member]
Debt Instrument [Line Items]
Revolving Line of Credit	2,000,000
Maximum borrowing capacity	40,000,000
Term Loan Foreign [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 13,000,000
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	6.37%		3.36%
Debt Instrument, Basis Spread on Variable Rate	2.00%
Foreign Line of Credit [Member]
Debt Instrument [Line Items]
Revolving Line of Credit	$ 2,500,000
Existing Term Loan [Member]
Debt Instrument [Line Items]
Loans Payable				$ 6,750,000
Term Loan [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate	40000.00%
Line of Credit [Member] \| Foreign Line of Credit [Member]
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 10,000,000
First Amendment [Member] \| Domestic Line of Credit [Member]
Debt Instrument [Line Items]
Maximum borrowing capacity	32,500,000
Interest Rate Swap Domestic [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	25,000,000
Interest Rate Swap Foreign [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	10,000,000
Interest Rate Swap [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 35,000,000
Term Loan [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	6.40%		4.34%
Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Restrictive Covenants	7500000
Maximum [Member] \| Term Loan [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate	40000.00%
Minimum [Member] \| Term Loan [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate	17500.00%
Liability [Member] \| Interest Rate Swap [Member]
Debt Instrument [Line Items]
Foreign Currency Contracts, Liability, Fair Value Disclosure	$ 787,000		$ 65,000
Scenario, Forecast [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Restrictive Covenants		12500000