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Commitments and Contingencies - Additional Information (Detail) $ in Millions | 12 Months Ended
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Dec. 31, 2017 USD ($)
Schedule Of Commitments And Contingencies [Line Items] |
Change in warranty reserve for disclosure purposes only | $ 2.8
Minimum [Member] |
Schedule Of Commitments And Contingencies [Line Items] |
Average period for PE material purchases under short-term supply contracts for which pricing is negotiated as needed | 1 year
Maximum [Member] |
Schedule Of Commitments And Contingencies [Line Items] |
Average period for PE material purchases under short-term supply contracts for which pricing is negotiated as needed | 2 years
Surface Flaking Warranty Reserve [Member] |
Schedule Of Commitments And Contingencies [Line Items] |
Percentage change in warranty claims used as a threshold for disclosure | 10.00%
Residential Use [Member] |
Schedule Of Commitments And Contingencies [Line Items] |
Warranty period | 25 years
Commercial Use [Member] |
Schedule Of Commitments And Contingencies [Line Items] |
Warranty period | 10 years
Transcend, Enhance, Select and Universal Fascia Product [Member] | Residential Use [Member] |
Schedule Of Commitments And Contingencies [Line Items] |
Warranty period | 25 years
Transcend, Enhance, Select and Universal Fascia Product [Member] | Commercial Use [Member] |
Schedule Of Commitments And Contingencies [Line Items] |
Warranty period | 10 years
Trex Signature Railing [Member] | Residential Use [Member] |
Schedule Of Commitments And Contingencies [Line Items] |
Warranty period | 25 years
Trex Signature Railing [Member] | Commercial Use [Member] |
Schedule Of Commitments And Contingencies [Line Items] |
Warranty period | 25 years
Raw Material Supply Contracts [Member] |
Schedule Of Commitments And Contingencies [Line Items] |
Purchase commitment | $ 47.2
Purchase commitment, due in second year | 9.5
Purchase commitment, due in third year | $ 5.9

X
- Definition Average period for PE material purchases under short term supply contracts for which pricing is negotiated as needed. + References No definition available. + Details
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Namespace Prefix: | trex_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage change in the expected number of remaining claims to be settled with payment or the expected cost to settle claims used as a threshold for disclosure. + References No definition available. + Details
Name: | trex_PercentSensitivityChangeInExpectedSurfaceFlakingClaims
Namespace Prefix: | trex_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Schedule of commitments and contingencies. + References No definition available. + Details
Name: | trex_ScheduleOfCommitmentsAndContingenciesLineItems
Namespace Prefix: | trex_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Estimated change in the warranty reserve resulting from a 10% change in the expected number of remaining claims to be settled with payment or the expected cost to settle claims for disclosure purposes only. + References No definition available. + Details
Name: | trex_SensitivityChangeInSurfaceFlakingWarrantyReserve
Namespace Prefix: | trex_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The number of years the Company warrants that its products will be free from material defects in workmanship and materials. + References No definition available. + Details
Name: | trex_WarrantyPeriod
Namespace Prefix: | trex_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Minimum amount of purchase arrangement maturing in the next fiscal year following the latest fiscal year. Includes, but not limited to, recorded and unrecorded purchase obligations, long-term purchase commitments, and short-term purchase commitments. + References No definition available. + Details
Name: | us-gaap_PurchaseObligationDueInNextTwelveMonths
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Minimum amount of purchase arrangement maturing in the second fiscal year following the latest fiscal year. Includes, but not limited to, recorded and unrecorded purchase obligations, long-term purchase commitments, and short-term purchase commitments. + References No definition available. + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Minimum amount of purchase arrangement maturing in the third fiscal year following the latest fiscal year. Includes, but not limited to, recorded and unrecorded purchase obligations, long-term purchase commitments, and short-term purchase commitments. + References No definition available. + Details
Name: | us-gaap_PurchaseObligationDueInThirdYear
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Details
Name: | us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ValuationAllowancesAndReservesTypeAxis=trex_SurfaceFlakingWarrantyReserveMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_GuaranteeObligationsByNatureAxis=trex_ResidentialUseMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_GuaranteeObligationsByNatureAxis=trex_CommercialUseMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LongTermPurchaseCommitmentByCategoryOfItemPurchasedAxis=trex_RawMaterialSupplyContractsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |