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Stock-Based Compensation - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified | 0 Months Ended | 12 Months Ended | 0 Months Ended | 12 Months Ended
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May 07, 2014 | Dec. 31, 2014 | Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Shares of common stock that may be issued under the plan adjusted to reflect stock split | 2 us-gaap_StockholdersEquityNoteStockSplitConversionRatio1 |  |  |  |
Approximate number of shares employees purchased under the Employee Stock Purchase Plan |  | 407,000 trex_StockIssuedSharesEmployeeStockPurchasePlan |  |  |
2014 Stock Incentive Plan [Member] |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Total aggregate number of shares of common stock that may be issued |  | 6,420,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized / us-gaap_PlanNameAxis = trex_TwoThousandFourteenStockIncentivePlanMember | 6,420,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized / us-gaap_PlanNameAxis = trex_TwoThousandFourteenStockIncentivePlanMember |  |
Increase in number of shares of common stock from the previous plan that may be issued |  | 60,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized / us-gaap_PlanNameAxis = trex_TwoThousandFourteenStockIncentivePlanMember |  |  |
Shares of common stock that may be issued under the plan adjusted to reflect stock split | 2 us-gaap_StockholdersEquityNoteStockSplitConversionRatio1 / us-gaap_PlanNameAxis = trex_TwoThousandFourteenStockIncentivePlanMember |  |  |  |
Time-Based Restricted Stock [Member] |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Total fair value of restricted shares vested |  | 3.9 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue / us-gaap_AwardTypeAxis = trex_TimeBasedRestrictedStockMember |  | $ 3.1 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue / us-gaap_AwardTypeAxis = trex_TimeBasedRestrictedStockMember | $ 2.5 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue / us-gaap_AwardTypeAxis = trex_TimeBasedRestrictedStockMember
Unrecognized compensation cost related to unvested awards |  | 2.8 us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions / us-gaap_AwardTypeAxis = trex_TimeBasedRestrictedStockMember | 2.8 us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions / us-gaap_AwardTypeAxis = trex_TimeBasedRestrictedStockMember |  |
Compensation cost recognition period for unvested awards |  |  | 1 year 6 months |  |
Number of shares vested |  | 116,641 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod / us-gaap_AwardTypeAxis = trex_TimeBasedRestrictedStockMember |  | 139,594 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod / us-gaap_AwardTypeAxis = trex_TimeBasedRestrictedStockMember | 189,410 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod / us-gaap_AwardTypeAxis = trex_TimeBasedRestrictedStockMember
Performance-Based Restricted Stock [Member] |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Unrecognized compensation cost related to unvested awards |  | 0.6 us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions / us-gaap_AwardTypeAxis = trex_PerformanceBasedRestrictedStockMember | 0.6 us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions / us-gaap_AwardTypeAxis = trex_PerformanceBasedRestrictedStockMember |  |
Compensation cost recognition period for unvested awards |  |  | 1 year 7 months 6 days |  |
Vesting period |  | 3 years |  |  |
Number of shares vested |  | 0 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod / us-gaap_AwardTypeAxis = trex_PerformanceBasedRestrictedStockMember |  |  |
Stock Appreciation Rights [Member] |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Unrecognized compensation cost related to unvested awards |  | 0.5 us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions / us-gaap_AwardTypeAxis = us-gaap_StockAppreciationRightsSARSMember | $ 0.5 us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions / us-gaap_AwardTypeAxis = us-gaap_StockAppreciationRightsSARSMember |  |
Compensation cost recognition period for unvested awards |  |  | 6 years 6 months |  |
Maximum contractual term |  | 10 years |  |  |
Weighted-average fair value of grants |  | 17.78 trex_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionGrantsInPeriodWeightedAverageGrantDateFairValuePerPricingModel / us-gaap_AwardTypeAxis = us-gaap_StockAppreciationRightsSARSMember |  | $ 11.67 trex_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionGrantsInPeriodWeightedAverageGrantDateFairValuePerPricingModel / us-gaap_AwardTypeAxis = us-gaap_StockAppreciationRightsSARSMember | $ 7.06 trex_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionGrantsInPeriodWeightedAverageGrantDateFairValuePerPricingModel / us-gaap_AwardTypeAxis = us-gaap_StockAppreciationRightsSARSMember
Employee Stock Purchase Plan [Member] |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Total aggregate number of shares of common stock that may be issued |  | 600,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized / us-gaap_AwardTypeAxis = trex_EmployeeStockPurchasePlanMember | 600,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized / us-gaap_AwardTypeAxis = trex_EmployeeStockPurchasePlanMember |  |
Shares of common stock that may be issued under the plan adjusted to reflect stock split | 2 us-gaap_StockholdersEquityNoteStockSplitConversionRatio1 / us-gaap_AwardTypeAxis = trex_EmployeeStockPurchasePlanMember |  |  |  |
Percentage of market price on lesser of either first day of calendar quarter or last day of calendar quarter for purchase price |  | 85.00%us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent / us-gaap_AwardTypeAxis = trex_EmployeeStockPurchasePlanMember |  |  |
Percentage of gross compensation eligible employees may elect to participate in the plan |  | 15.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumEmployeeSubscriptionRate / us-gaap_AwardTypeAxis = trex_EmployeeStockPurchasePlanMember | 15.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumEmployeeSubscriptionRate / us-gaap_AwardTypeAxis = trex_EmployeeStockPurchasePlanMember |  |
Stock Options [Member] |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Maximum contractual term |  | 10 years |  |  |
Share-Based Compensation Award, Tranche One [Member] | Performance-Based Restricted Stock [Member] |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Stock-based Compensation vesting percentage |  | 33.33%us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage / us-gaap_AwardTypeAxis = trex_PerformanceBasedRestrictedStockMember / us-gaap_VestingAxis = us-gaap_ShareBasedCompensationAwardTrancheOneMember |  |  |
Share-Based Compensation Award, Tranche Two [Member] | Performance-Based Restricted Stock [Member] |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Stock-based Compensation vesting percentage |  | 33.33%us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage / us-gaap_AwardTypeAxis = trex_PerformanceBasedRestrictedStockMember / us-gaap_VestingAxis = us-gaap_ShareBasedCompensationAwardTrancheTwoMember |  |  |
Share-Based Compensation Award, Tranche Three [Member] | Performance-Based Restricted Stock [Member] |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Stock-based Compensation vesting percentage |  | 33.33%us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage / us-gaap_AwardTypeAxis = trex_PerformanceBasedRestrictedStockMember / us-gaap_VestingAxis = us-gaap_ShareBasedCompensationAwardTrancheThreeMember |  |  |
Minimum [Member] | Performance-Based Restricted Stock [Member] |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Percentage of target number of shares that will vest |  | 0.00%trex_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentageToTargetNumberOfShares / us-gaap_AwardTypeAxis = trex_PerformanceBasedRestrictedStockMember / us-gaap_RangeAxis = us-gaap_MinimumMember |  |  |
Maximum [Member] | Performance-Based Restricted Stock [Member] |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Percentage of target number of shares that will vest |  | 200.00%trex_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentageToTargetNumberOfShares / us-gaap_AwardTypeAxis = trex_PerformanceBasedRestrictedStockMember / us-gaap_RangeAxis = us-gaap_MaximumMember |  |  |

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- Definition With respect to each vesting, the number of shares that will vest stated as a percentage of the target number of shares. + References No definition available. + Details
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- Definition The weighted average grant-date fair value of equity instruments other than options granted during the reporting period as calculated by applying the disclosed option pricing methodology. + References No definition available. + Details
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- Definition Number of shares issued since the plan's inception as a result of an employee stock purchase plan. + References No definition available. + Details
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- Definition Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (i) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Unrecognized cost of unvested share-based awards, other than options, awarded to employees as compensation. + References No definition available. + Details
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- Definition Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Percentage of vesting of share-based compensation awards. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(iii)(2) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (d)(2) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(2) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition The highest percentage of annual salary that an employee is permitted to utilize with respect to the plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Number of additional shares authorized for issuance under an established share-based compensation plan. + References No definition available. + Details
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- Definition The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Purchase price of common stock expressed as a percentage of its fair value. + References No definition available. + Details
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- Definition Ratio applied to the conversion of stock split, for example but not limited to, one share converted to two or two shares converted to one. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Stock Split -URI http://asc.fasb.org/extlink&oid=6525746 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section S99 -Paragraph 4 -Subparagraph (SAB TOPIC 4.C) -URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187143-122770 + Details
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