Critical Accounting Policy (Notes)	3 Months Ended
Mar. 31, 2018
Accounting Policies [Abstract]
Significant Accounting Policies [Text Block]	The preparation of these consolidated financial statements requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. On an on-going basis, management evaluates its estimates and judgments. Management bases its estimates and judgments on historical experience and on various other factors that are believed to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying value of assets and liabilities that are not readily apparent from other sources. Actual results may differ from these estimates under different assumptions or conditions. Management believes the following critical accounting policies, among others, affect its more significant judgments and estimates used in the preparation of its consolidated financial statements. Revenue Recognition: The Company historically has recognized revenue from two streams, product revenue and tooling revenue. Product revenue is earned from the manufacture and sale of sheet molding compound and thermoset and thermoplastic products. Revenue from product sales is generally recognized as products are shipped, as the Company transfers title and risk of ownership to the customer and is entitled to payment upon shipment. In limited circumstances, the Company recognizes revenue from product sales when products are produced and the customer takes title and risk of ownership at our production facility. Tooling revenue is earned from manufacturing multiple tools, molds and assembly equipment as part of a tooling program for a customer. Given that the Company is providing a significant service of producing highly interdependent component parts of the tooling program, each tooling program consists of a single performance obligation to provide the customer the capability to produce a single product. Based on the arrangement with the customer, the Company recognizes revenue either at a point in time or over time. When the Company does not have an enforceable right to payment, the Company recognizes tooling revenue at a point in time. In such cases, the Company recognizes revenue upon customer acceptance, which is when the customer has legal title to the tools. The Company historically recognized all tooling revenue at a point in time, upon customer acceptance, before the adoption of ASU 2014-09. Certain tooling programs include an enforceable right to payment. In those cases, the Company recognizes revenue over time based on the extent of progress towards completion of its performance obligation. The Company uses a cost-to-cost measure of progress for such contracts because it best depicts the transfer of value to the customer and also correlates with the amount of consideration to which the entity expects to be entitled in exchange for transferring the promised goods or services to the customer. Under the cost-to-cost measure of progress, progress towards completion is measured based on the ratio of costs incurred to date to the total estimated costs at completion of the performance obligation. Revenues are recorded proportionally as costs are incurred. Income taxes: The Company’s consolidated balance sheets include a net non-current deferred tax liability of $395,000 at March 31, 2018 and December 31, 2017. The Company evaluates the balance of deferred tax assets that will be realized based on the premise that the Company is more likely than not to realize deferred tax benefits through the generation of future taxable income. For more information, refer to Note 11 of the Notes to Consolidated Financial Statements contained in the Company's 2017 Annual Report to Shareholders on Form 10-K. Accounts receivable allowances: Management maintains allowances for doubtful accounts for estimated losses resulting from the inability of its customers to make required payments. If the financial condition of the Company’s customers were to deteriorate, resulting in an impairment of their ability to make payments, additional allowances may be required. The Company has determined that no allowance for doubtful accounts was needed at March 31, 2018 and December 31, 2017, respectively. Management also records estimates for chargebacks for customer returns and deductions, discounts offered to customers, and price adjustments. Should customer chargebacks fluctuate from the estimated amounts, additional allowances may be required. The Company reduced accounts receivable for chargebacks by $1,493,000 at March 31, 2018 and $857,000 at December 31, 2017. Inventories: Inventories, which include material, labor and manufacturing overhead, are valued at the lower of cost or net realizable value. The inventories are accounted for using the first-in, first-out (FIFO) method of determining inventory costs. Inventory quantities on-hand are regularly reviewed, and where necessary, provisions for excess and obsolete inventory are recorded based on historical and anticipated usage. The Company has recorded an allowance for slow moving and obsolete inventory of $973,000 at March 31, 2018 and $624,000 at December 31, 2017. Contract Assets/Liabilities: Contract assets and liabilities represent the net cumulative customer billings, vendor payments and revenue recognized for tooling programs. For tooling programs where net revenue recognized and vendor payments exceed customer billings, the Company recognizes a contract asset. For tooling programs where net customer billings exceed revenue recognized and vendor payments, the Company recognizes a contract liability. Customer payment terms vary by contract and can range from progress payments based on work performed or one single payment once the contract is completed. Contract assets are generally classified as current. The Company has recorded contract assets in prepaid expenses and other current assets on the Consolidated Balance Sheet. During the three months ended March 31, 2018, the Company recognized no impairments on contract assets. Contract liabilities are also generally classified as current. The Company has recorded contract liabilities in other current liabilities on the Consolidated Balance Sheet. In the first quarter of 2017, the Company recognized revenue of $520,000 related to contract liabilities. Derivative instruments: Derivative instruments are utilized to manage exposure to fluctuations in foreign currency exchange rates and interest rates. All derivative instruments are formally documented as cash flow hedges and are recorded at fair value at each reporting period. Gains and losses related to currency forward contracts and interest rate swaps are deferred and recorded as a component of Accumulated Other Comprehensive Income in the Consolidated Statement of Stockholders' Equity and then subsequently recognized in the Consolidated Statement of Income when the hedged item affects net income. The ineffective portion of the change in fair value of a hedge is recognized in income immediately. For additional information on derivative instruments, see Note 14. Long-Lived Assets: Long-lived assets consist primarily of property, plant and equipment and definite-lived intangibles. The recoverability of long-lived assets is evaluated by an analysis of operating results and consideration of other significant events or changes in the business environment. The Company evaluates whether impairment exists for property, plant and equipment on the basis of undiscounted expected future cash flows from operations before interest. There was no impairment of the Company's long-lived assets for the three months ended March 31, 2018 or March 31, 2017. Goodwill and Other Intangibles: The Company evaluates goodwill annually on December 31st to determine whether impairment exists, or at interim periods if an indicator of possible impairment exists. The Company evaluates goodwill for impairment utilizing the one-step qualitative assessment. The Company considers relevant events and circumstances that affect the fair value or carrying amount of the Company. Such events and circumstances could include macroeconomic conditions, industry and market conditions, cost factors, overall financial performance, entity specific events and capital markets pricing. The Company places more weight on the events and circumstances that most affect the Company's fair value or carrying amount. These factors are all considered by management in reaching its conclusion about whether to perform the first step of the impairment test. If the Company's fair value is determined to be more likely than not impaired based on the one-step qualitative approach, a quantitative valuation to estimate the fair value of the Company is performed. Fair value measurements are based on a projected discounted cash flow valuation model, in accordance with ASC 350, “Intangibles-Goodwill and Other.” There was no impairment of the Company's goodwill for the year ended December 31, 2017, and no indicators of impairment for the three months ended March 31, 2018. Self-Insurance: The Company is self-insured with respect to its Columbus and Batavia, Ohio, Gaffney, South Carolina, Winona, Minnesota and Brownsville, Texas medical, dental and vision claims and Columbus and Batavia, Ohio workers’ compensation claims, all of which are subject to stop-loss insurance thresholds. The Company is also self-insured for dental and vision with respect to its Cobourg, Canada location. The Company has recorded an estimated liability for self-insured medical, dental, vision and worker’s compensation claims incurred but not reported at March 31, 2018 and December 31, 2017 of $959,000 and $862,000, respectively. Post-retirement benefits: Management records an accrual for post-retirement costs associated with the health care plan sponsored by Core Molding Technologies. Should actual results differ from the assumptions used to determine the reserves, additional provisions may be required. In particular, increases in future healthcare costs above the assumptions could have an adverse effect on Core Molding Technologies’ operations. The effect of a change in healthcare costs is described in Note 12 of the Notes to Consolidated Financial Statements contained in the Company's 2017 Annual Report to Shareholders on Form 10-K. Core Molding Technologies had a liability for post retirement healthcare benefits based on actuarially computed estimates of $9,049,000 at March 31, 2018 and $9,050,000 at December 31, 2017.

The preparation of these consolidated financial statements requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. On an on-going basis, management evaluates its estimates and judgments. Management bases its estimates and judgments on historical experience and on various other factors that are believed to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying value of assets and liabilities that are not readily apparent from other sources. Actual results may differ from these estimates under different assumptions or conditions.

Management believes the following critical accounting policies, among others, affect its more significant judgments and estimates used in the preparation of its consolidated financial statements.

Revenue Recognition: The Company historically has recognized revenue from two streams, product revenue and tooling revenue. Product revenue is earned from the manufacture and sale of sheet molding compound and thermoset and thermoplastic products. Revenue from product sales is generally recognized as products are shipped, as the Company transfers title and risk of ownership to the customer and is entitled to payment upon shipment. In limited circumstances, the Company recognizes revenue from product sales when products are produced and the customer takes title and risk of ownership at our production facility.

Tooling revenue is earned from manufacturing multiple tools, molds and assembly equipment as part of a tooling program for a customer. Given that the Company is providing a significant service of producing highly interdependent component parts of the tooling program, each tooling program consists of a single performance obligation to provide the customer the capability to produce a single product. Based on the arrangement with the customer, the Company recognizes revenue either at a point in time or over time. When the Company does not have an enforceable right to payment, the Company recognizes tooling revenue at a point in time. In such cases, the Company recognizes revenue upon customer acceptance, which is when the customer has legal title to the tools. The Company historically recognized all tooling revenue at a point in time, upon customer acceptance, before the adoption of ASU 2014-09.

Certain tooling programs include an enforceable right to payment. In those cases, the Company recognizes revenue over time based on the extent of progress towards completion of its performance obligation. The Company uses a cost-to-cost measure of progress for such contracts because it best depicts the transfer of value to the customer and also correlates with the amount of consideration to which the entity expects to be entitled in exchange for transferring the promised goods or services to the customer. Under the cost-to-cost measure of progress, progress towards completion is measured based on the ratio of costs incurred to date to the total estimated costs at completion of the performance obligation. Revenues are recorded proportionally as costs are incurred.

Income taxes: The Company’s consolidated balance sheets include a net non-current deferred tax liability of $395,000 at March 31, 2018 and December 31, 2017. The Company evaluates the balance of deferred tax assets that will be realized based on the premise that the Company is more likely than not to realize deferred tax benefits through the generation of future taxable income. For more information, refer to Note 11 of the Notes to Consolidated Financial Statements contained in the Company's 2017 Annual Report to Shareholders on Form 10-K.

Accounts receivable allowances: Management maintains allowances for doubtful accounts for estimated losses resulting from the inability of its customers to make required payments. If the financial condition of the Company’s customers were to deteriorate, resulting in an impairment of their ability to make payments, additional allowances may be required. The Company has determined that no allowance for doubtful accounts was needed at March 31, 2018 and December 31, 2017, respectively. Management also records estimates for chargebacks for customer returns and deductions, discounts offered to customers, and price adjustments. Should customer chargebacks fluctuate from the estimated amounts, additional allowances may be required. The Company reduced accounts receivable for chargebacks by $1,493,000 at March 31, 2018 and $857,000 at December 31, 2017.

Inventories: Inventories, which include material, labor and manufacturing overhead, are valued at the lower of cost or net realizable value. The inventories are accounted for using the first-in, first-out (FIFO) method of determining inventory costs. Inventory quantities on-hand are regularly reviewed, and where necessary, provisions for excess and obsolete inventory are recorded based on historical and anticipated usage. The Company has recorded an allowance for slow moving and obsolete inventory of $973,000 at March 31, 2018 and $624,000 at December 31, 2017.

Contract Assets/Liabilities: Contract assets and liabilities represent the net cumulative customer billings, vendor payments and revenue recognized for tooling programs. For tooling programs where net revenue recognized and vendor payments exceed customer billings, the Company recognizes a contract asset. For tooling programs where net customer billings exceed revenue recognized and vendor payments, the Company recognizes a contract liability. Customer payment terms vary by contract and can range from progress payments based on work performed or one single payment once the contract is completed. Contract assets are generally classified as current. The Company has recorded contract assets in prepaid expenses and other current assets on the Consolidated Balance Sheet. During the three months ended March 31, 2018, the Company recognized no impairments on contract assets. Contract liabilities are also generally classified as current. The Company has recorded contract liabilities in other current liabilities on the Consolidated Balance Sheet. In the first quarter of 2017, the Company recognized revenue of $520,000 related to contract liabilities.

Derivative instruments: Derivative instruments are utilized to manage exposure to fluctuations in foreign currency exchange rates and interest rates. All derivative instruments are formally documented as cash flow hedges and are recorded at fair value at each reporting period. Gains and losses related to currency forward contracts and interest rate swaps are deferred and recorded as a component of Accumulated Other Comprehensive Income in the Consolidated Statement of Stockholders' Equity and then subsequently recognized in the Consolidated Statement of Income when the hedged item affects net income. The ineffective portion of the change in fair value of a hedge is recognized in income immediately. For additional information on derivative instruments, see Note 14.

Long-Lived Assets: Long-lived assets consist primarily of property, plant and equipment and definite-lived intangibles. The recoverability of long-lived assets is evaluated by an analysis of operating results and consideration of other significant events or changes in the business environment. The Company evaluates whether impairment exists for property, plant and equipment on the basis of undiscounted expected future cash flows from operations before interest. There was no impairment of the Company's long-lived assets for the three months ended March 31, 2018 or March 31, 2017.

Goodwill and Other Intangibles: The Company evaluates goodwill annually on December 31st to determine whether impairment exists, or at interim periods if an indicator of possible impairment exists. The Company evaluates goodwill for impairment utilizing the one-step qualitative assessment. The Company considers relevant events and circumstances that affect the fair value or carrying amount of the Company. Such events and circumstances could include macroeconomic conditions, industry and market conditions, cost factors, overall financial performance, entity specific events and capital markets pricing. The Company places more weight on the events and circumstances that most affect the Company's fair value or carrying amount. These factors are all considered by management in reaching its conclusion about whether to perform the first step of the impairment test.

If the Company's fair value is determined to be more likely than not impaired based on the one-step qualitative approach, a quantitative valuation to estimate the fair value of the Company is performed. Fair value measurements are based on a projected discounted cash flow valuation model, in accordance with ASC 350, “Intangibles-Goodwill and Other.”

There was no impairment of the Company's goodwill for the year ended December 31, 2017, and no indicators of impairment for the three months ended March 31, 2018.

Self-Insurance: The Company is self-insured with respect to its Columbus and Batavia, Ohio, Gaffney, South Carolina, Winona, Minnesota and Brownsville, Texas medical, dental and vision claims and Columbus and Batavia, Ohio workers’ compensation claims, all of which are subject to stop-loss insurance thresholds. The Company is also self-insured for dental and vision with respect to its Cobourg, Canada location. The Company has recorded an estimated liability for self-insured medical, dental, vision and worker’s compensation claims incurred but not reported at March 31, 2018 and December 31, 2017 of $959,000 and $862,000, respectively.

Post-retirement benefits: Management records an accrual for post-retirement costs associated with the health care plan sponsored by Core Molding Technologies. Should actual results differ from the assumptions used to determine the reserves, additional provisions may be required. In particular, increases in future healthcare costs above the assumptions could have an adverse effect on Core Molding Technologies’ operations. The effect of a change in healthcare costs is described in Note 12 of the Notes to Consolidated Financial Statements contained in the Company's 2017 Annual Report to Shareholders on Form 10-K. Core Molding Technologies had a liability for post retirement healthcare benefits based on actuarially computed estimates of $9,049,000 at March 31, 2018 and $9,050,000 at December 31, 2017.