Basis of Presentation	3 Months Ended
Mar. 31, 2018
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Basis of Presentation	1. Basis of Presentation Builders FirstSource, Inc., a Delaware corporation formed in 1998, is a leading supplier and manufacturer of building materials, manufactured components and construction services to professional homebuilders, sub-contractors, remodelers and consumers. The Company operates 402 locations in 40 states across the United States. In this quarterly report, references to the “Company,” “we,” “our,” “ours” or “us” refer to Builders FirstSource, Inc. and its consolidated subsidiaries unless otherwise stated or the context otherwise requires. In the opinion of management, the accompanying unaudited condensed consolidated financial statements include all recurring adjustments and normal accruals necessary for a fair statement of the Company’s financial position, results of operations and cash flows for the dates and periods presented. Results for interim periods are not necessarily indicative of the results to be expected during the remainder of the current year or for any future period. Intercompany transactions are eliminated in consolidation. The condensed consolidated balance sheet as of December 31, 2017 is derived from the audited consolidated financial statements but does not include all disclosures required by accounting principles generally accepted in the United States of America. This condensed consolidated balance sheet as of December 31, 2017 and the unaudited condensed consolidated financial statements included herein should be read in conjunction with the more detailed audited consolidated financial statements for the year ended December 31, 2017 included in our most recent annual report on Form 10-K. Accounting policies used in the preparation of these unaudited condensed consolidated financial statements are consistent with the accounting policies described in the Notes to Consolidated Financial Statements included in our Form 10-K. Recent Accounting Pronouncements In May 2017, the Financial Accounting Standards Board (“FASB”) issued an update to the existing guidance under the Compensation-Stock Compensation topic of the Accounting Standards Codification (“Codification”) to clarify when modification accounting would be applied for a change to the terms or conditions of a share-based award. Under this new guidance modification accounting is required only if the fair value, the vesting conditions, or the classification of the award changes as a result of the change in terms or conditions. This guidance was required to be adopted on a prospective basis for annual periods beginning on or after December 15, 2017. As such, the Company adopted this guidance on January 1, 2018. The adoption of this guidance did not have an impact on our financial statements. In January 2017, the FASB issued an update to the existing guidance under the Business Combinations topic of the Codification. This update revises the definition of a business. Under this guidance when substantially all of the assets acquired are concentrated in a single asset (or group of similar assets) the assets acquired would not be considered a business. If this initial screen is met the need for further assessment is eliminated. If this screen is not met in order to be considered a business an acquisition would have to include an input and a substantive process that together significantly contribute to the ability to create outputs. This update was required to be adopted by public companies on a prospective basis for annual and interim reporting periods beginning after December 15, 2017. As such, the Company adopted this guidance on January 1, 2018. The adoption of this guidance did not have an impact on our financial statements. In February 2016, the FASB issued an update to the existing guidance under the Leases topic of the Codification. Under the new guidance, lessees will be required to recognize the following for all leases, with the exception of short-term leases, at the commencement date: (1) a lease liability, which is a lessee‘s obligation to make lease payments arising from a lease, measured on a discounted basis; and (2) a right-of-use asset, which is an asset that represents the lessee’s right to use, or control the use of, a specified asset for the lease term. This update requires a modified retrospective transition as of the beginning of the earliest comparative period presented in the financial statements. This update is effective for public companies for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years, with early adoption permitted. The Company intends to adopt this guidance on a modified retrospective basis on January 1, 2019. We also intend to elect certain of the transition practical expedients permitted under this new guidance. The FASB issued a proposed update in January 2018 which, if ultimately adopted by the FASB, would allow an entity to elect an option to apply the transition provisions prospectively as of the effective date of the new standard rather than as of the earliest comparative period presented. If the FASB adopts this proposed update in its current form, we will re-evaluate to determine which transition option we will elect. The Company has a significant number of leases, primarily related to real estate and rolling stock, which are accounted for as operating leases under existing guidance. While we are currently evaluating the impact of this new guidance on our financial statements, we are expecting a significant impact to our balance sheet upon adoption related to the establishment of lease liabilities and the corresponding right-of-use assets. We are also currently assessing and updating our business processes, systems and controls to ensure compliance with the accounting and disclosure requirements of the new standard upon adoption. In May 2014, the FASB issued an update to the existing guidance under the Revenue Recognition topic of the Codification which is a comprehensive new revenue recognition model requiring a company to recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. Subsequent to issuance of the original update, the FASB issued several further updates amending this new guidance. In April 2016, the FASB issued an update clarifying issues related to identifying performance obligations and licensing. In May 2016, the FASB issued an update regarding the assessment of collectability criteria, presentation of sales taxes, measurement of noncash consideration and transition guidance for completed contracts and contract modifications. Under previous guidance, we recognized sales from contracts with service elements on the completed contract method when these contracts were completed within 30 days. The remaining contracts with service elements were recognized under the percentage of completion method. On January 1, 2018 we adopted this guidance on a modified retrospective basis for contracts which were not completed as of January 1, 2018. Under this updated guidance, revenue related to our contracts with service elements is now recognized over time based on the extent of progress towards completion of the performance obligation because of continuous transfer of control to the customer. We have assessed and updated our business processes, systems and controls to ensure compliance with the recognition and disclosure requirements of the new standard. Results for periods beginning on or after January 1, 2018 are presented in accordance with this new guidance. Results for prior periods have not been adjusted and continue to be presented under previous guidance. Upon adoption, the Company recognized a $2.0 million ($1.5 million net of taxes) impact to the beginning balance of our accumulated deficit through a cumulative effect adjustment related to the unrecognized portion of contracts previously accounted for under the completed contract method of revenue recognition.

1. Basis of Presentation

Builders FirstSource, Inc., a Delaware corporation formed in 1998, is a leading supplier and manufacturer of building materials, manufactured components and construction services to professional homebuilders, sub-contractors, remodelers and consumers. The Company operates 402 locations in 40 states across the United States. In this quarterly report, references to the “Company,” “we,” “our,” “ours” or “us” refer to Builders FirstSource, Inc. and its consolidated subsidiaries unless otherwise stated or the context otherwise requires.

In the opinion of management, the accompanying unaudited condensed consolidated financial statements include all recurring adjustments and normal accruals necessary for a fair statement of the Company’s financial position, results of operations and cash flows for the dates and periods presented. Results for interim periods are not necessarily indicative of the results to be expected during the remainder of the current year or for any future period. Intercompany transactions are eliminated in consolidation.

The condensed consolidated balance sheet as of December 31, 2017 is derived from the audited consolidated financial statements but does not include all disclosures required by accounting principles generally accepted in the United States of America. This condensed consolidated balance sheet as of December 31, 2017 and the unaudited condensed consolidated financial statements included herein should be read in conjunction with the more detailed audited consolidated financial statements for the year ended December 31, 2017 included in our most recent annual report on Form 10-K. Accounting policies used in the preparation of these unaudited condensed consolidated financial statements are consistent with the accounting policies described in the Notes to Consolidated Financial Statements included in our Form 10-K.

Recent Accounting Pronouncements

In May 2017, the Financial Accounting Standards Board (“FASB”) issued an update to the existing guidance under the Compensation-Stock Compensation topic of the Accounting Standards Codification (“Codification”) to clarify when modification accounting would be applied for a change to the terms or conditions of a share-based award. Under this new guidance modification accounting is required only if the fair value, the vesting conditions, or the classification of the award changes as a result of the change in terms or conditions. This guidance was required to be adopted on a prospective basis for annual periods beginning on or after December 15, 2017. As such, the Company adopted this guidance on January 1, 2018. The adoption of this guidance did not have an impact on our financial statements.

In January 2017, the FASB issued an update to the existing guidance under the Business Combinations topic of the Codification. This update revises the definition of a business. Under this guidance when substantially all of the assets acquired are concentrated in a single asset (or group of similar assets) the assets acquired would not be considered a business. If this initial screen is met the need for further assessment is eliminated. If this screen is not met in order to be considered a business an acquisition would have to include an input and a substantive process that together significantly contribute to the ability to create outputs. This update was required to be adopted by public companies on a prospective basis for annual and interim reporting periods beginning after December 15, 2017. As such, the Company adopted this guidance on January 1, 2018. The adoption of this guidance did not have an impact on our financial statements.

In February 2016, the FASB issued an update to the existing guidance under the Leases topic of the Codification. Under the new guidance, lessees will be required to recognize the following for all leases, with the exception of short-term leases, at the commencement date: (1) a lease liability, which is a lessee‘s obligation to make lease payments arising from a lease, measured on a discounted basis; and (2) a right-of-use asset, which is an asset that represents the lessee’s right to use, or control the use of, a specified asset for the lease term. This update requires a modified retrospective transition as of the beginning of the earliest comparative period presented in the financial statements. This update is effective for public companies for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years, with early adoption permitted. The Company intends to adopt this guidance on a modified retrospective basis on January 1, 2019. We also intend to elect certain of the transition practical expedients permitted under this new guidance.

The FASB issued a proposed update in January 2018 which, if ultimately adopted by the FASB, would allow an entity to elect an option to apply the transition provisions prospectively as of the effective date of the new standard rather than as of the earliest comparative period presented. If the FASB adopts this proposed update in its current form, we will re-evaluate to determine which transition option we will elect.

The Company has a significant number of leases, primarily related to real estate and rolling stock, which are accounted for as operating leases under existing guidance. While we are currently evaluating the impact of this new guidance on our financial statements, we are expecting a significant impact to our balance sheet upon adoption related to the establishment of lease liabilities and the corresponding right-of-use assets. We are also currently assessing and updating our business processes, systems and controls to ensure compliance with the accounting and disclosure requirements of the new standard upon adoption.

In May 2014, the FASB issued an update to the existing guidance under the Revenue Recognition topic of the Codification which is a comprehensive new revenue recognition model requiring a company to recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. Subsequent to issuance of the original update, the FASB issued several further updates amending this new guidance. In April 2016, the FASB issued an update clarifying issues related to identifying performance obligations and licensing. In May 2016, the FASB issued an update regarding the assessment of collectability criteria, presentation of sales taxes, measurement of noncash consideration and transition guidance for completed contracts and contract modifications. Under previous guidance, we recognized sales from contracts with service elements on the completed contract method when these contracts were completed within 30 days. The remaining contracts with service elements were recognized under the percentage of completion method.

On January 1, 2018 we adopted this guidance on a modified retrospective basis for contracts which were not completed as of January 1, 2018. Under this updated guidance, revenue related to our contracts with service elements is now recognized over time based on the extent of progress towards completion of the performance obligation because of continuous transfer of control to the customer. We have assessed and updated our business processes, systems and controls to ensure compliance with the recognition and disclosure requirements of the new standard.

Results for periods beginning on or after January 1, 2018 are presented in accordance with this new guidance. Results for prior periods have not been adjusted and continue to be presented under previous guidance. Upon adoption, the Company recognized a $2.0 million ($1.5 million net of taxes) impact to the beginning balance of our accumulated deficit through a cumulative effect adjustment related to the unrecognized portion of contracts previously accounted for under the completed contract method of revenue recognition.