ACCOUNTING POLICIES (Policies)	12 Months Ended
Dec. 31, 2012
ACCOUNTING POLICIES [Abstract]
Principles of Consolidation	Principles of Consolidation The Consolidated Financial Statements included in this report have been prepared by management of LMI Aerospace, Inc. All significant intercompany balances and transactions have been eliminated in consolidation.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America requires management to make certain estimates and assumptions. These estimates and assumptions affect the reported amounts in the financial statements and accompanying notes. Actual results could differ from these estimates.
Revenue Recognition	Revenue Recognition Except as described below, the Company recognizes revenue for sales of products and related services when products are delivered and services are rendered, the price is fixed or determinable, and collection is reasonably assured. The majority of the Aerostructures segment's revenues are recognized when products are shipped, delivery has occurred or services have been rendered. For long-term contracts requiring development and delivery of multiple units of product over more than one year, the Company incurs and defers, as part of inventory, certain costs which are specific to the contract and will be recouped as part of the unit cost charged to the customer under the contract. Such costs are charged to cost of product sales ratably as the manufactured units are shipped pursuant to the contract. Changes in the estimated number of units expected to be delivered under such contracts result in prospective adjustments of the ratable charge-off of deferred inventoriable costs per unit shipped. Should the remaining inventoriable costs plus estimated costs of production of units yet to be shipped under the contract exceed estimated future contract revenues, the resulting full loss is recognized in the period it becomes probable and estimable. No such loss was recognized in 2012, 2011, or 2010. The majority of the Engineering Services segment's revenues are generated under cost-plus reimbursement contracts. Revenue for cost-plus reimbursement contracts is recognized as labor hours and direct costs are incurred. Such revenues include the value of labor hours at pre-negotiated rates, estimated overhead and general and administrative costs allocable to the contract based on applicable rates for each quarter, actual direct incidental costs, and a pre-negotiated fee markup or margin. For certain long-term fixed price design and development contracts, the Company applies the percentage of completion method of contract accounting. The cost-to-cost method is used to measure progress toward completion. Under the cost-to-cost method of accounting, the Company recognizes sales based on the ratio of costs incurred to the estimate of total costs at completion. No such loss was recognized in 2012, 2011, or 2010. For certain other contracts, progress is measured using the units of delivery method. The amount reported as revenue represents the invoice price of delivered products, and cost of sales is determined by applying the estimated gross margin percentage to the amount of revenue recognized. Should estimated total costs at completion exceed the estimated total revenue, the anticipated full loss is recognized in the period in which it is estimated. In the ordinary course of business, the Company may receive requests from its customers to perform tasks not specified in its contracts. When this occurs on a long-term contract using the cost-to-cost method of percentage of completion accounting, the Company may record revenue for claims or unpriced change orders to be negotiated with customers. As of December 31, 2012, approximately 0.5% of revenue represented amounts associated with claims and unpriced change orders.
Pre-Contract and Pre-Production Costs under Long-Term Supply Contracts	Pre-Contract and Pre-Production Costs under Long-Term Supply Contracts In certain circumstances, the Company capitalizes costs incurred prior to the execution of a contract with the customer. These circumstances are limited to instances in which the Company has substantially negotiated the terms and conditions of the anticipated contract with its customers and concluded that their recoverability from the anticipated contract is probable. As these costs are directly associated with a specific anticipated contract and they are concluded to be recoverable under that anticipated contract, the Company has capitalized these amounts. The Company may incur design and development costs prior to the production phase of contracts that are outside the scope of the contract accounting method. These pre-production costs are generally related to costs the Company incurs to design and build tooling that is owned by the customer and design and engineering services. The Company receives the non-cancellable right to use these tools to build the parts as specified in a contractual agreement and therefore has capitalized these costs. In certain instances, the Company enters into agreements with its customers that provide it a contractual guarantee for reimbursement of design and engineering services incurred prior to the production phase of a contract. Due to the contractual guarantee, the Company capitalizes the costs of these services. The pre-production costs are amortized to cost of sales over the shorter of the life of the contractual agreement or the related tooling.
Cash and Cash Equivalents	Cash and Cash Equivalents Cash and cash equivalents include cash on hand, deposits in transit and all highly liquid investment instruments with an initial maturity of three months or less.
Inventories	Inventories The Company's inventories are stated at the lower of cost or market and utilize actual costs for raw materials and an average cost for work in process, manufactured and purchased components and finished goods. The Company evaluates the inventory carrying value and reduces the carrying costs based on customer activity, estimated future demand, price deterioration, and other relevant information. The Company's customer demand is unpredictable and may fluctuate due to factors beyond the Company's control. In addition, inventoried costs include capitalized contract costs relating to programs and contracts with long-term production cycles, a portion of which is not expected to be realized within one year. See further discussion regarding deferred long-term contract costs under "Revenue Recognition" and "Pre-Contract and Pre-Production Costs under Long-Term Supply Contracts."
Allowance for Doubtful Accounts	Allowance for Doubtful Accounts The allowance for doubtful accounts receivable reflects the Company's best estimate of probable losses inherent in its accounts receivable. The basis used to determine this value is derived from historical experience, specific allowances for known troubled customers and other currently available information.
Property, Plant and Equipment	Property, Plant and Equipment Property, plant and equipment are stated at cost. Depreciation is calculated using the straight-line method over the estimated useful lives of the related assets. Leasehold improvements are amortized using the straight-line method over the shorter of the lease term or the estimated useful lives of the assets. Estimated useful lives for buildings, machinery and equipment, and purchased software are 20 to 35 years, 4 to 10 years and 3 to 4 years, respectively. Amortization incurred under capital leases is reported with depreciation expense.
Long-Lived Assets	Long Lived Assets Long lived assets held and used are reviewed for impairment whenever events or changes in circumstances indicate that the carrying value of an asset may not be recoverable.
Goodwill and Intangible Assets	Goodwill and Intangible Assets The Company's acquisitions involve the purchase of tangible and intangible assets and the assumption of certain liabilities. As part of the purchase price allocation, the Company allocates the purchase price to the tangible assets acquired and liabilities assumed based on estimated fair market values, and the remainder of the purchase price is allocated to intangibles and goodwill. Goodwill and intangible assets with indefinite lives are not amortized but are subject to an impairment assessment at least annually in relation to their fair value. As part of this process, the Company first assesses qualitatively whether it is necessary to perform the quantitative test. The qualitative assessment involves evaluating relevant events or circumstances to determine whether it is more likely than not that the fair value of the reporting unit is less than its carrying amount. If it is not, the Company can bypass the quantitative assessment of goodwill. If it is, or if the Company has elected to bypass the qualitative assessment process, the quantitative assessment of goodwill utilizes a two-step process, where the carrying value of the reporting unit is compared to its fair value. If the carrying value is less than the fair value, no impairment exists, and the second step is not performed. However, if the carrying value is greater than the fair value, the second step is performed. An impairment charge would be recognized for the amount that the carrying value of the goodwill exceeds its fair value.
Deferred Gain on Sale of Real Estate	Deferred Gain on Sale of Real Estate On December 28, 2006, the Company entered into an agreement with a third party to sell and lease back certain of its real estate properties for $10,250. The amount of the sale price in excess of book value for these properties of $4,242 was deferred and is being amortized over the 18 year term of the leases on a straight-line basis.
Share-based Compensation	Share-Based Compensation The Company recognizes compensation expense for share-based payment transactions in the financial statements at their fair value. The expense is measured at the grant date, based on the calculated fair value of the share-based award, and is recognized over the requisite service period (generally the vesting period of the equity award).
Income Taxes	Income Taxes Provisions for federal and state income taxes are calculated on reported net income before income taxes based on current tax law and also include, in the current period, the cumulative effect of any changes in tax rates from those used previously in determining deferred tax assets and liabilities. Such provisions differ from the amounts currently receivable or payable because certain items of income and expense are recognized in different time periods for financial reporting purposes than for income tax purposes. Significant judgment is required in determining income tax provisions and evaluating tax positions. The accounting for uncertainty in income taxes requires a more-likely-than-not threshold for financial statement recognition and measurement of tax positions taken or expected to be taken in a tax return. The Company records a liability for the difference between the benefit recognized and measured for financial statement purposes and the tax position taken or expected to be taken on our tax return. To the extent that management's assessment of such tax positions changes, the change in estimate is recorded in the period in which the determination is made. The Company's unrecognized tax benefits as of December 31, 2012 and 2011 are immaterial. The Company expects no significant increases or decreases in unrecognized tax benefits due to changes in tax positions within one year of December 31, 2012. The Company has no material interest or penalties relating to income taxes recognized on the balance sheets as of December 31, 2012, and 2011. As of December 31, 2012, returns for calendar years 2009 through 2011 remain subject to examination by the Internal Revenue Service and/or various state tax jurisdictions.
Financial Instruments	Financial Instruments Fair values of the Company's long-term obligations approximate their carrying values as the applicable interest rates approximate the current market rates or have variable rate characteristics. The Company's other financial instruments have fair values that approximate their respective carrying values due to their short maturities.
Reclassifications	Reclassifications Certain reclassifications have been made to prior period financial statements in order to conform to current period presentation.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In October 2012, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") No. 2012-04, "Technical Corrections and Improvements,"("ASU 2012-04"). ASU 2012-04 amends current guidance by clarifying the FASB Accounting Standards Codification ("Codification"), correcting unintended application of guidance, or making minor improvements to the Codification. These amendments are not expected to have a significant effect on current accounting practice or create a significant administrative cost to most entities. Additionally, the amendments included in ASU 2012-04 intend to make the Codification easier to understand and the fair value measurement guidance easier to apply by eliminating inconsistencies and providing needed clarifications. The amendments in ASU 2012-04 that will not have transition guidance will be effective upon issuance. For public entities, the amendments that are subject to the transition guidance will be effective for fiscal periods beginning after December 15, 2012. The adoption of this standard is not expected to have a material effect on our consolidated financial statements. In January 2013, the FASB issued ASU No. 2013-01, "Balance Sheet (Topic 210): Clarifying the Scope of Disclosures about Offsetting Assets and Liabilities" to clarify the scope of the disclosure requirements described in the FASB's ASU No. 2011-11"Balance Sheet: Disclosures about Offsetting Assets and Liabilities" ("ASU 2011-11"). ASU No. 2011-11 requires an entity to disclose information about offsetting and related arrangements to enable users of its financial statements to understand the effect of those arrangements on its financial position. This update clarifies that the scope is limited to include derivatives or securities borrowing and lending transactions that are offset or subject to an enforceable master netting arrangement or similar agreement. These updates are effective for fiscal years, and interim periods within those years, beginning on or after January 1, 2013 applied retrospectively for comparative periods presented. The adoption of this standard is not expected to have a material effect on our consolidated financial statements. In February 2013, the FASB issued ASU No. 2013-02, "Comprehensive Income (Topic 220): Reporting of Amounts Reclassified Out of Accumulated Other Comprehensive Income." The standard requires companies to present, either in a single note or parenthetically on the face of the financial statements; the effect of significant amounts reclassified from each component of accumulated other comprehensive income based on its source and the income statement line items affected by the reclassification. This ASU is effective prospectively for reporting periods beginning after December 15, 2012 which corresponds to the Company's first fiscal quarter beginning January 1, 2013. The adoption of this is not expected to have a material effect on our consolidated financial statements.

ACCOUNTING POLICIES (Policies)

12 Months Ended

Dec. 31, 2012

The Consolidated Financial Statements included in this report have been prepared by management of LMI Aerospace, Inc. All significant intercompany balances and transactions have been eliminated in consolidation.

Use of Estimates

The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America requires management to make certain estimates and assumptions. These estimates and assumptions affect the reported amounts in the financial statements and accompanying notes. Actual results could differ from these estimates.

Revenue Recognition

Except as described below, the Company recognizes revenue for sales of products and related services when products are delivered and services are rendered, the price is fixed or determinable, and collection is reasonably assured.

The majority of the Aerostructures segment's revenues are recognized when products are shipped, delivery has occurred or services have been rendered. For long-term contracts requiring development and delivery of multiple units of product over more than one year, the Company incurs and defers, as part of inventory, certain costs which are specific to the contract and will be recouped as part of the unit cost charged to the customer under the contract. Such costs are charged to cost of product sales ratably as the manufactured units are shipped pursuant to the contract. Changes in the estimated number of units expected to be delivered under such contracts result in prospective adjustments of the ratable charge-off of deferred inventoriable costs per unit shipped. Should the remaining inventoriable costs plus estimated costs of production of units yet to be shipped under the contract exceed estimated future contract revenues, the resulting full loss is recognized in the period it becomes probable and estimable. No such loss was recognized in 2012, 2011, or 2010.

The majority of the Engineering Services segment's revenues are generated under cost-plus reimbursement contracts. Revenue for cost-plus reimbursement contracts is recognized as labor hours and direct costs are incurred. Such revenues include the value of labor hours at pre-negotiated rates, estimated overhead and general and administrative costs allocable to the contract based on applicable rates for each quarter, actual direct incidental costs, and a pre-negotiated fee markup or margin.

For certain long-term fixed price design and development contracts, the Company applies the percentage of completion method of contract accounting. The cost-to-cost method is used to measure progress toward completion. Under the cost-to-cost method of accounting, the Company recognizes sales based on the ratio of costs incurred to the estimate of total costs at completion. No such loss was recognized in 2012, 2011, or 2010. For certain other contracts, progress is measured using the units of delivery method. The amount reported as revenue represents the invoice price of delivered products, and cost of sales is determined by applying the estimated gross margin percentage to the amount of revenue recognized. Should estimated total costs at completion exceed the estimated total revenue, the anticipated full loss is recognized in the period in which it is estimated.

In the ordinary course of business, the Company may receive requests from its customers to perform tasks not specified in its contracts. When this occurs on a long-term contract using the cost-to-cost method of percentage of completion accounting, the Company may record revenue for claims or unpriced change orders to be negotiated with customers. As of December 31, 2012, approximately 0.5% of revenue represented amounts associated with claims and unpriced change orders.

Pre-Contract and Pre-Production Costs under Long-Term Supply Contracts

In certain circumstances, the Company capitalizes costs incurred prior to the execution of a contract with the customer. These circumstances are limited to instances in which the Company has substantially negotiated the terms and conditions of the anticipated contract with its customers and concluded that their recoverability from the anticipated contract is probable. As these costs are directly associated with a specific anticipated contract and they are concluded to be recoverable under that anticipated contract, the Company has capitalized these amounts.

The Company may incur design and development costs prior to the production phase of contracts that are outside the scope of the contract accounting method. These pre-production costs are generally related to costs the Company incurs to design and build tooling that is owned by the customer and design and engineering services. The Company receives the non-cancellable right to use these tools to build the parts as specified in a contractual agreement and therefore has capitalized these costs. In certain instances, the Company enters into agreements with its customers that provide it a contractual guarantee for reimbursement of design and engineering services incurred prior to the production phase of a contract. Due to the contractual guarantee, the Company capitalizes the costs of these services. The pre-production costs are amortized to cost of sales over the shorter of the life of the contractual agreement or the related tooling.

Cash and Cash Equivalents

Cash and cash equivalents include cash on hand, deposits in transit and all highly liquid investment instruments with an initial maturity of three months or less.

Inventories

The Company's inventories are stated at the lower of cost or market and utilize actual costs for raw materials and an average cost for work in process, manufactured and purchased components and finished goods. The Company evaluates the inventory carrying value and reduces the carrying costs based on customer activity, estimated future demand, price deterioration, and other relevant information. The Company's customer demand is unpredictable and may fluctuate due to factors beyond the Company's control. In addition, inventoried costs include capitalized contract costs relating to programs and contracts with long-term production cycles, a portion of which is not expected to be realized within one year. See further discussion regarding deferred long-term contract costs under "Revenue Recognition" and "Pre-Contract and Pre-Production Costs under Long-Term Supply Contracts."

Allowance for Doubtful Accounts

The allowance for doubtful accounts receivable reflects the Company's best estimate of probable losses inherent in its accounts receivable. The basis used to determine this value is derived from historical experience, specific allowances for known troubled customers and other currently available information.

Property, Plant and Equipment

Property, plant and equipment are stated at cost. Depreciation is calculated using the straight-line method over the estimated useful lives of the related assets. Leasehold improvements are amortized using the straight-line method over the shorter of the lease term or the estimated useful lives of the assets. Estimated useful lives for buildings, machinery and equipment, and purchased software are 20 to 35 years, 4 to 10 years and 3 to 4 years, respectively. Amortization incurred under capital leases is reported with depreciation expense.

Long-Lived Assets

Long Lived Assets

Long lived assets held and used are reviewed for impairment whenever events or changes in circumstances indicate that the carrying value of an asset may not be recoverable.

Goodwill and Intangible Assets

The Company's acquisitions involve the purchase of tangible and intangible assets and the assumption of certain liabilities. As part of the purchase price allocation, the Company allocates the purchase price to the tangible assets acquired and liabilities assumed based on estimated fair market values, and the remainder of the purchase price is allocated to intangibles and goodwill. Goodwill and intangible assets with indefinite lives are not amortized but are subject to an impairment assessment at least annually in relation to their fair value. As part of this process, the Company first assesses qualitatively whether it is necessary to perform the quantitative test. The qualitative assessment involves evaluating relevant events or circumstances to determine whether it is more likely than not that the fair value of the reporting unit is less than its carrying amount. If it is not, the Company can bypass the quantitative assessment of goodwill. If it is, or if the Company has elected to bypass the qualitative assessment process, the quantitative assessment of goodwill utilizes a two-step process, where the carrying value of the reporting unit is compared to its fair value. If the carrying value is less than the fair value, no impairment exists, and the second step is not performed. However, if the carrying value is greater than the fair value, the second step is performed. An impairment charge would be recognized for the amount that the carrying value of the goodwill exceeds its fair value.

Deferred Gain on Sale of Real Estate

On December 28, 2006, the Company entered into an agreement with a third party to sell and lease back certain of its real estate properties for $10,250. The amount of the sale price in excess of book value for these properties of $4,242 was deferred and is being amortized over the 18 year term of the leases on a straight-line basis.

Share-based Compensation

Share-Based Compensation

The Company recognizes compensation expense for share-based payment transactions in the financial statements at their fair value. The expense is measured at the grant date, based on the calculated fair value of the share-based award, and is recognized over the requisite service period (generally the vesting period of the equity award).

Income Taxes

Provisions for federal and state income taxes are calculated on reported net income before income taxes based on current tax law and also include, in the current period, the cumulative effect of any changes in tax rates from those used previously in determining deferred tax assets and liabilities. Such provisions differ from the amounts currently receivable or payable because certain items of income and expense are recognized in different time periods for financial reporting purposes than for income tax purposes. Significant judgment is required in determining income tax provisions and evaluating tax positions.

The accounting for uncertainty in income taxes requires a more-likely-than-not threshold for financial statement recognition and measurement of tax positions taken or expected to be taken in a tax return. The Company records a liability for the difference between the benefit recognized and measured for financial statement purposes and the tax position taken or expected to be taken on our tax return. To the extent that management's assessment of such tax positions changes, the change in estimate is recorded in the period in which the determination is made.

The Company's unrecognized tax benefits as of December 31, 2012 and 2011 are immaterial. The Company expects no significant increases or decreases in unrecognized tax benefits due to changes in tax positions within one year of December 31, 2012. The Company has no material interest or penalties relating to income taxes recognized on the balance sheets as of December 31, 2012, and 2011. As of December 31, 2012, returns for calendar years 2009 through 2011 remain subject to examination by the Internal Revenue Service and/or various state tax jurisdictions.

Financial Instruments

Fair values of the Company's long-term obligations approximate their carrying values as the applicable interest rates approximate the current market rates or have variable rate characteristics. The Company's other financial instruments have fair values that approximate their respective carrying values due to their short maturities.

Reclassifications

Certain reclassifications have been made to prior period financial statements in order to conform to current period presentation.

Recent Accounting Pronouncements

In October 2012, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") No. 2012-04, "Technical Corrections and Improvements,"("ASU 2012-04"). ASU 2012-04 amends current guidance by clarifying the FASB Accounting Standards Codification ("Codification"), correcting unintended application of guidance, or making minor improvements to the Codification. These amendments are not expected to have a significant effect on current accounting practice or create a significant administrative cost to most entities. Additionally, the amendments included in ASU 2012-04 intend to make the Codification easier to understand and the fair value measurement guidance easier to apply by eliminating inconsistencies and providing needed clarifications. The amendments in ASU 2012-04 that will not have transition guidance will be effective upon issuance. For public entities, the amendments that are subject to the transition guidance will be effective for fiscal periods beginning after December 15, 2012. The adoption of this standard is not expected to have a material effect on our consolidated financial statements.

In January 2013, the FASB issued ASU No. 2013-01, "Balance Sheet (Topic 210): Clarifying the Scope of Disclosures about Offsetting Assets and Liabilities" to clarify the scope of the disclosure requirements described in the FASB's ASU No. 2011-11"Balance Sheet: Disclosures about Offsetting Assets and Liabilities" ("ASU 2011-11"). ASU No. 2011-11 requires an entity to disclose information about offsetting and related arrangements to enable users of its financial statements to understand the effect of those arrangements on its financial position. This update clarifies that the scope is limited to include derivatives or securities borrowing and lending transactions that are offset or subject to an enforceable master netting arrangement or similar agreement. These updates are effective for fiscal years, and interim periods within those years, beginning on or after January 1, 2013 applied retrospectively for comparative periods presented. The adoption of this standard is not expected to have a material effect on our consolidated financial statements.

In February 2013, the FASB issued ASU No. 2013-02, "Comprehensive Income (Topic 220): Reporting of Amounts Reclassified Out of Accumulated Other Comprehensive Income." The standard requires companies to present, either in a single note or parenthetically on the face of the financial statements; the effect of significant amounts reclassified from each component of accumulated other comprehensive income based on its source and the income statement line items affected by the reclassification. This ASU is effective prospectively for reporting periods beginning after December 15, 2012 which corresponds to the Company's first fiscal quarter beginning January 1, 2013. The adoption of this is not expected to have a material effect on our consolidated financial statements.