XML 63 R56.htm IDEA: XBRL DOCUMENT
v3.20.1

Summary of Significant Accounting Policies Foreign Currency Adjustments (Details) - USD ($) | 12 Months Ended
--- | ---
Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Accounting Policies [Abstract] |  |  |
Net foreign translation and transaction activity | $ 229,000 | $ 88,000 | $ 30,000

X
- Definition Net foreign translation and transaction activity + References No definition available. + Details
Name: | cmt_Netforeigntranslationandtransactionactivity
Namespace Prefix: | cmt_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_AccountingPoliciesAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration