Significant Accounting Policies (Policies)	9 Months Ended
Sep. 30, 2020
Accounting Policies [Abstract]
Basis of Accounting, Policy [Policy Text Block]	Basis of Presentation: We have prepared our unaudited condensed consolidated financial statements in accordance with Rule 10-01 of Regulation S-X for interim financial statements. These statements do not include all information and footnotes that generally accepted accounting principles require for complete annual financial statements. However, the information in these statements reflects all normal recurring adjustments which are, in our opinion, necessary for a fair presentation of the results for the interim periods. The results of operations for the three and nine months ended September 30, 2020 are not necessarily indicative of the results that will be realized for the fiscal year ending December 31, 2020. We have derived our condensed consolidated balance sheet as of December 31, 2019 from the audited consolidated financial statements for the year ended December 31, 2019. You should read these condensed consolidated financial statements in conjunction with the audited consolidated financial statements and notes thereto for the year ended December 31, 2019. The consolidated financial statements include the accounts of MRC Global Inc. and its wholly owned and majority owned subsidiaries (collectively referred to as the “Company” or by such terms as “we,” “our” or “us”). All material intercompany balances and transactions have been eliminated in consolidation.
New Accounting Pronouncements, Policy [Policy Text Block]	Recent Issued Accounting Pronouncements: In August 2020, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2020-06, Debt – Debt with Conversion and Other Options and Derivative Hedging – Contracts in Entity’s Own Equity (Subtopic 815-40) ("ASU 2020-06"), which simplifies guidance on the topics of convertible instruments, derivative contracts and earnings per share ("EPS") calculations. This update will be effective for fiscal years beginning after December 15, 2021, and interim periods within those fiscal years. We are currently evaluating the impacts of the provisions of ASU 2020-06 on our consolidated financial statements. In March 2020, the FASB issued Accounting Standards Update ASU 2020-04, Reference Rate Reform (Topic 848) ("ASU 2020-04"), which provides optional expedients and exceptions for applying U.S. GAAP to contracts, hedging relationships, and other transactions affected by the discontinuation of certain reference rates, including the London Interbank Offered Rate ("LIBOR"). The amendments are effective for all entities as of March 12, 2020 through December 31, 2022. We are currently evaluating the impacts of the provisions of ASU 2020-04 on our consolidated financial statements. In December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes, an update intended to simplify various aspects related to accounting for income taxes. This guidance removes certain exceptions to the general principles in Topic 740 and clarifies and amends existing guidance to improve consistent application. This accounting standards update will be effective for annual and interim financial statement periods beginning after December 15, 2020, with early adoption permitted. We are currently evaluating the impact of this accounting standards update, but do not expect the adoption to materially impact our consolidated financial statements. Adoption of New Accounting Standards: In June 2016, the FASB issued ASU 2016-13, Measurement of Credit Losses on Financial Instruments, which requires that an entity measure impairment of certain financial instruments, including trade receivables, based on expected losses rather than incurred losses. We adopted ASU 2016-13 on January 1, 2020. The adoption of this new standard resulted in the recognition of $1 million of incremental bad debt expense in the nine months ended September 30, 2020.

Significant Accounting Policies (Policies)

9 Months Ended

Sep. 30, 2020

Basis of Accounting, Policy [Policy Text Block]

Basis of Presentation: We have prepared our unaudited condensed consolidated financial statements in accordance with Rule 10-01 of Regulation S-X for interim financial statements. These statements do not include all information and footnotes that generally accepted accounting principles require for complete annual financial statements. However, the information in these statements reflects all normal recurring adjustments which are, in our opinion, necessary for a fair presentation of the results for the interim periods. The results of operations for the three and nine months ended September 30, 2020 are not necessarily indicative of the results that will be realized for the fiscal year ending December 31, 2020. We have derived our condensed consolidated balance sheet as of December 31, 2019 from the audited consolidated financial statements for the year ended December 31, 2019. You should read these condensed consolidated financial statements in conjunction with the audited consolidated financial statements and notes thereto for the year ended December 31, 2019.

The consolidated financial statements include the accounts of MRC Global Inc. and its wholly owned and majority owned subsidiaries (collectively referred to as the “Company” or by such terms as “we,” “our” or “us”). All material intercompany balances and transactions have been eliminated in consolidation.

New Accounting Pronouncements, Policy [Policy Text Block]

Recent Issued Accounting Pronouncements: In August 2020, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2020-06, Debt – Debt with Conversion and Other Options and Derivative Hedging – Contracts in Entity’s Own Equity (Subtopic 815-40) ("ASU 2020-06"), which simplifies guidance on the topics of convertible instruments, derivative contracts and earnings per share ("EPS") calculations. This update will be effective for fiscal years beginning after December 15, 2021, and interim periods within those fiscal years. We are currently evaluating the impacts of the provisions of ASU 2020-06 on our consolidated financial statements.

In March 2020, the FASB issued Accounting Standards Update ASU 2020-04, Reference Rate Reform (Topic 848) ("ASU 2020-04"), which provides optional expedients and exceptions for applying U.S. GAAP to contracts, hedging relationships, and other transactions affected by the discontinuation of certain reference rates, including the London Interbank Offered Rate ("LIBOR"). The amendments are effective for all entities as of March 12, 2020 through December 31, 2022. We are currently evaluating the impacts of the provisions of ASU 2020-04 on our consolidated financial statements.

In December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes, an update intended to simplify various aspects related to accounting for income taxes. This guidance removes certain exceptions to the general principles in Topic 740 and clarifies and amends existing guidance to improve consistent application. This accounting standards update will be effective for annual and interim financial statement periods beginning after December 15, 2020, with early adoption permitted. We are currently evaluating the impact of this accounting standards update, but do not expect the adoption to materially impact our consolidated financial statements.

Adoption of New Accounting Standards: In June 2016, the FASB issued ASU 2016-13, Measurement of Credit Losses on Financial Instruments, which requires that an entity measure impairment of certain financial instruments, including trade receivables, based on expected losses rather than incurred losses. We adopted ASU 2016-13 on January 1, 2020. The adoption of this new standard resulted in the recognition of $1 million of incremental bad debt expense in the nine months ended September 30, 2020.