NEW ACCOUNTING STANDARDS (Policies)	9 Months Ended
Sep. 30, 2018
Accounting Policies [Abstract]
New Accounting Standards	NEW ACCOUNTING STANDARDS In March 2017, the Financial Accounting Standards Board (FASB) issued Accounting Standard Update (ASU) 2017-07, Compensation Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost (ASU 2017-07). This ASU improves the presentation of net periodic pension cost and net periodic postretirement benefit cost. The effective date of this ASU was for fiscal years and interim periods beginning after December 15, 2017. The Company adopted this ASU as of January 1, 2018. This ASU was applied retrospectively for the presentation of the net periodic postretirement cost components in the Condensed Consolidated Statement of Earnings for the three and nine months ended September 30, 2017 and prospectively, after the effective date. The guidance limiting the capitalization of net periodic benefit cost in assets to the service cost component is applied prospectively. The impact of the ASU for the three and nine months ended September 30, 2017 was an increase of $3.4 million and $9.4 million, respectively, in Selling, general and administrative expenses (SG&A) offset by a reduction in Total other expense, net of $3.4 million and $9.4 million, respectively, related to the reclassification of interest cost, expected return on plan assets and amortization of unrecognized gains and prior service credits. See Note 8 to the Financial Statements. In February 2018, the FASB issued ASU 2018-02, Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income. This ASU allows a reclassification from Accumulated other comprehensive earnings to Retained earnings for stranded tax effects resulting from the 2017 Tax Cuts and Jobs Act. The effective date of this ASU is for fiscal years and interim periods beginning after December 15, 2018, and early adoption is permitted. The Company has evaluated the provisions of this standard and is in the process of assessing the amount to reclassify from Accumulated other comprehensive losses to Retained earnings. In August 2018, the FASB issued ASU 2018-14, Retirement Benefits - Defined Benefit Plans - Changes to the Disclosure Requirements for Defined Benefit Plans. This ASU removes disclosures that are no longer considered cost beneficial, clarifies specific requirements of the disclosure and adds disclosure requirements identified as relevant to improve the effectiveness of the disclosures. The effective date of this ASU is for fiscal years and interim periods beginning after December 15, 2020 and early adoption is permitted. The Company is evaluating the impact of this ASU. In September 2018, the FASB issued ASU 2018-15, Intangibles - Goodwill and Other Internal Use Software (Subtopic 350-40) Customer's Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That is a Service Contract. This ASU aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software. The effective date of this ASU is for fiscal years and interim periods beginning after December 15, 2019, and early adoption is permitted. The Company has elected to early adopt prospectively and does not expect a material impact to the Company's Consolidated Financial Statements. LEASE ACCOUNTING STANDARDS In February 2016, the FASB issued ASU 2016-02, Leases as modified by subsequently issued ASUs 2018-01, 2018-10 and 2018-11. The core principle of the ASU improves transparency and comparability related to the accounting and reporting of leasing arrangements, including balance sheet recognition for assets and liabilities associated with rights and obligations created by leases with terms greater than twelve months, among other changes. The effective date of these ASUs is for fiscal years and interim periods beginning after December 15, 2018 and early adoption is permitted. The Company has elected not to early adopt these ASUs. The Company plans to elect the modified retrospective application with practical expedient to adopt the new guidance effective January 1, 2019. Grainger will record the right of use assets and corresponding liabilities and does not expect a material impact to the Company's Consolidated Financial Statements.

NEW ACCOUNTING STANDARDS

In March 2017, the Financial Accounting Standards Board (FASB) issued Accounting Standard Update (ASU) 2017-07, Compensation Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost (ASU 2017-07). This ASU improves the presentation of net periodic pension cost and net periodic postretirement benefit cost. The effective date of this ASU was for fiscal years and interim periods beginning after December 15, 2017. The Company adopted this ASU as of January 1, 2018. This ASU was applied retrospectively for the presentation of the net periodic postretirement cost components in the Condensed Consolidated Statement of Earnings for the three and nine months ended September 30, 2017 and prospectively, after the effective date. The guidance limiting the capitalization of net periodic benefit cost in assets to the service cost component is applied prospectively. The impact of the ASU for the three and nine months ended September 30, 2017 was an increase of $3.4 million and $9.4 million, respectively, in Selling, general and administrative expenses (SG&A) offset by a reduction in Total other expense, net of $3.4 million and $9.4 million, respectively, related to the reclassification of interest cost, expected return on plan assets and amortization of unrecognized gains and prior service credits. See Note 8 to the Financial Statements.

In February 2018, the FASB issued ASU 2018-02, Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income. This ASU allows a reclassification from Accumulated other comprehensive earnings to Retained earnings for stranded tax effects resulting from the 2017 Tax Cuts and Jobs Act. The effective date of this ASU is for fiscal years and interim periods beginning after December 15, 2018, and early adoption is permitted. The

Company has evaluated the provisions of this standard and is in the process of assessing the amount to reclassify from Accumulated other comprehensive losses to Retained earnings.

In August 2018, the FASB issued ASU 2018-14, Retirement Benefits - Defined Benefit Plans - Changes to the Disclosure Requirements for Defined Benefit Plans. This ASU removes disclosures that are no longer considered cost beneficial, clarifies specific requirements of the disclosure and adds disclosure requirements identified as relevant to improve the effectiveness of the disclosures. The effective date of this ASU is for fiscal years and interim periods beginning after December 15, 2020 and early adoption is permitted. The Company is evaluating the impact of this ASU.

In September 2018, the FASB issued ASU 2018-15, Intangibles - Goodwill and Other Internal Use Software (Subtopic 350-40) Customer's Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That is a Service Contract. This ASU aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software. The effective date of this ASU is for fiscal years and interim periods beginning after December 15, 2019, and early adoption is permitted. The Company has elected to early adopt prospectively and does not expect a material impact to the Company's Consolidated Financial Statements.

LEASE ACCOUNTING STANDARDS

In February 2016, the FASB issued ASU 2016-02, Leases as modified by subsequently issued ASUs 2018-01, 2018-10 and 2018-11. The core principle of the ASU improves transparency and comparability related to the accounting and reporting of leasing arrangements, including balance sheet recognition for assets and liabilities associated with rights and obligations created by leases with terms greater than twelve months, among other changes.

The effective date of these ASUs is for fiscal years and interim periods beginning after December 15, 2018 and early adoption is permitted. The Company has elected not to early adopt these ASUs. The Company plans to elect the modified retrospective application with practical expedient to adopt the new guidance effective January 1, 2019. Grainger will record the right of use assets and corresponding liabilities and does not expect a material impact to the Company's Consolidated Financial Statements.