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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
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 2us-gaap_StockholdersEquityNoteStockSplitConversionRatio1        
Approximate number of shares employees purchased under the Employee Stock Purchase Plan   407,000trex_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   6,420,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized
/ us-gaap_PlanNameAxis
= trex_TwoThousandFourteenStockIncentivePlanMember
6,420,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized
/ us-gaap_PlanNameAxis
= trex_TwoThousandFourteenStockIncentivePlanMember
   
Increase in number of shares of common stock from the previous plan that may be issued   60,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized
/ us-gaap_PlanNameAxis
= trex_TwoThousandFourteenStockIncentivePlanMember
     
Shares of common stock that may be issued under the plan adjusted to reflect stock split 2us-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   3.9us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue
/ us-gaap_AwardTypeAxis
= trex_TimeBasedRestrictedStockMember
  $ 3.1us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue
/ us-gaap_AwardTypeAxis
= trex_TimeBasedRestrictedStockMember
$ 2.5us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue
/ us-gaap_AwardTypeAxis
= trex_TimeBasedRestrictedStockMember
Unrecognized compensation cost related to unvested awards   2.8us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions
/ us-gaap_AwardTypeAxis
= trex_TimeBasedRestrictedStockMember
2.8us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions
/ us-gaap_AwardTypeAxis
= trex_TimeBasedRestrictedStockMember
   
Compensation cost recognition period for unvested awards     1 year 6 months    
Number of shares vested   116,641us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod
/ us-gaap_AwardTypeAxis
= trex_TimeBasedRestrictedStockMember
  139,594us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod
/ us-gaap_AwardTypeAxis
= trex_TimeBasedRestrictedStockMember
189,410us-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   0.6us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions
/ us-gaap_AwardTypeAxis
= trex_PerformanceBasedRestrictedStockMember
0.6us-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   0us-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   0.5us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions
/ us-gaap_AwardTypeAxis
= us-gaap_StockAppreciationRightsSARSMember
$ 0.5us-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   17.78trex_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionGrantsInPeriodWeightedAverageGrantDateFairValuePerPricingModel
/ us-gaap_AwardTypeAxis
= us-gaap_StockAppreciationRightsSARSMember
  $ 11.67trex_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionGrantsInPeriodWeightedAverageGrantDateFairValuePerPricingModel
/ us-gaap_AwardTypeAxis
= us-gaap_StockAppreciationRightsSARSMember
$ 7.06trex_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   600,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized
/ us-gaap_AwardTypeAxis
= trex_EmployeeStockPurchasePlanMember
600,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized
/ us-gaap_AwardTypeAxis
= trex_EmployeeStockPurchasePlanMember
   
Shares of common stock that may be issued under the plan adjusted to reflect stock split 2us-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