SIGNIFICANT ACCOUNTING POLICIES (Policies)	9 Months Ended
SIGNIFICANT ACCOUNTING POLICIES (Policies)	Sep. 30, 2017
SIGNIFICANT ACCOUNTING POLICIES
Basis of Presentation	Basis of Presentation: The Condensed Consolidated Financial Statements are unaudited, and include the accounts of Matson and all wholly-owned subsidiaries, after elimination of significant intercompany amounts and transactions. Significant investments in businesses, partnerships, and limited liability companies in which the Company does not have a controlling financial interest, but has the ability to exercise significant influence, are accounted for under the equity method. A controlling financial interest is one in which the Company has a majority voting interest or one in which the Company is the primary beneficiary of a variable interest entity. The Company accounts for its investment in the Terminal Joint Venture using the equity method of accounting. The Condensed Consolidated Financial Statements include the accounts and activities of Span Alaska from the acquisition date on August 4, 2016 (see Note 13). Due to the nature of the Company’s operations, including the acquisition of Span Alaska on August 4, 2016, the results for interim periods are not necessarily indicative of results to be expected for the year. These Condensed Consolidated Financial Statements reflect all normal recurring adjustments that are, in the opinion of management, necessary for fair presentation of the results of the interim periods, and do not include all of the information and footnotes required by U.S. generally accepted accounting principles for complete consolidated financial statements. The Condensed Consolidated Financial Statements should be read in conjunction with the Consolidated Financial Statements and notes thereto included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2016, filed with the Securities and Exchange Commission (“SEC”) on February 24, 2017.
Fiscal Period	Fiscal Period: The period end for Matson covered by this report is September 30, 2017. The period end for MatNav and its subsidiaries covered by this report occurred on the last Friday in September, or September 29, 2017, for the third quarter 2017.
Significant Accounting Policies	Significant Accounting Policies: The Company’s significant accounting policies are described in Note 2 to the Consolidated Financial Statements included in Part II, Item 8 of the Company’s Annual Report on Form 10-K for the year ended December 31, 2016.
Immaterial Correction of an Error in Previously Issued Financial Statements	Immaterial Correction of an Error in Previously Issued Financial Statements: Subsequent to the filing of the Company’s Quarterly Report on Form 10-Q for the period ended June 30, 2017, the Company identified an error related to its post-retirement benefit plan liabilities. The Company did not account for the transfer of certain participants belonging to three stevedore union groups in Hawaii, out of the Company’s post-retirement benefit plan and into a multi-employer Stevedore Industry Committee Welfare Benefit Plan (“SIC Plan”), that was approved by the Board of the SIC Plan in August 2016 (the “Transfer”). The SIC Plan assumed the existing unfunded obligation related to the transferred participants who continue to receive substantially the same post-retirement benefits that they previously received under the Company’s post-retirement benefit plan. The Company determined that the Transfer should have been accounted for in August 2016 when the Transfer was approved by the SIC Board as a negative plan amendment in accordance with Accounting Standards Codification (“ASC”) 715-60, Defined Benefit Plans – Other Postretirements since the Company retains significant risks related to the obligation for the transferred participants’ benefits, and will continue to participate in the funding of the transferred benefit obligation through ongoing and increased contributions to the SIC Plan. Accordingly, the Company corrected this error by recording a decrease of $36.8 million in employee benefit plan liabilities and $1.6 million in accruals and other liabilities, with a corresponding net gain in prior service costs of $22.5 million in accumulated other comprehensive loss (gain), net of $15.0 million of deferred income taxes, and a $0.9 million increase in retained earnings as of December 31, 2016. The net gain in prior service costs included in accumulated other comprehensive loss will be amortized over a period of approximately 10 years. The correction for the amortization of the net gain in prior service costs resulted in an increase in Ocean Transportation segment operating income of $0.5 million, and income tax expense of $0.2 million in the Company’s Condensed Consolidated Financial Statements for the three and nine months ended September 30, 2016. The Company believes the correction of this error is immaterial to previously issued Consolidated Financial Statements for prior periods. The misstatement had no impact on the Company’s Condensed Consolidated Statements of Cash Flows.
Reclassifications	Reclassifications: Certain amounts included within cash flows from operating activities of the Condensed Consolidated Statement of Cash Flow for the nine months ended September 30, 2016, have been reclassified to conform to the current period presentation. There was no change in net cash provided by operating activities for the nine months ended September 30, 2016.
New Accounting Pronouncements	New Accounting Pronouncements: Revenue from Contracts with Customers: In May 2014, the Financial Accounting Standards Board (“FASB”) issued ASU 2014-09, “Revenue from Contracts with Customers (Topic 606)” (“ASU 2014-09”). ASU 2014-09 establishes principles regarding the nature, timing, and uncertainty of revenue from contracts with customers. It removes inconsistencies in existing revenue requirements, provides a more robust framework for addressing revenue issues and improves comparability of revenue recognition practices across entities, industries, jurisdictions and capital markets. ASU 2014-09 will be effective for interim and annual reporting periods beginning after December 15, 2017. The Company is in the process of evaluating the impact of adopting ASU 2014-09 on its Consolidated Financial Statements. The Company is currently reviewing customer contracts in each of its operating segments for all revenue generating services provided by the Company, and is assessing the impact of applying ASU 2014-09, and comparing this to the Company’s historical revenue recognition practices. Based upon the preliminary review of customer contracts, the Company believes that the Company’s revenue recognition policies are consistent with the requirements of ASU 2014-09. While the Company continues to assess all potential impacts of adopting ASU 2014-09, based upon information available to date, the Company does not expect the adoption of ASU 2014-09 to have a significant impact on either the timing or recognition of Ocean Transportation and Logistics revenues. The Company is also evaluating its accounting disclosures related to revenue recognition. The Company plans to adopt the requirements of the new standard by recording the impact of adoption as an adjustment to retained earnings at the beginning of the first quarter of 2018. Leases: In February 2016, the FASB issued ASU 2016-02, “Leases (Topic 842)” (“ASU 2016-02”), which requires lessees to record most leases on their balance sheets but recognize the expenses on their statements of income in a manner similar to current practice. ASU 2016-02 states that a lessee would recognize a lease liability for the obligation to make lease payments, and a right-of-use asset for the underlying leased asset for the period of the lease term. ASU 2016-02 will be effective for interim and annual periods beginning after December 15, 2018 and early adoption is permitted. The Company is in the process of evaluating the impact of adopting ASU 2016-02. Net Periodic Pension Cost and Benefit Cost: In March 2017, the FASB issued ASU 2017-07. “Compensation – Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Benefit Cost (“ASU 2017-07”). ASU 2017-07 requires employees that sponsor defined benefit pension and other post-retirement plans to present the service cost component of net benefit cost in the same income statement line item as other employee compensation costs arising from services rendered, and that only the service cost component will be eligible for capitalization. The other components of the net periodic benefit cost must be presented separately from the line item that includes the service cost component and outside of the income from operations subtotal. ASU 2017-07 is effective for interim and annual periods beginning after December 15, 2017. The Company does not expect the adoption of ASU 2017-07 to have a significant impact on the Company’s Consolidated Financial Statements.
Contingencies	Contingencies: Environmental Matters: The Company’s Ocean Transportation business has certain risks that could result in expenditures for environmental remediation. The Company believes that based on all information available to it, the Company is currently in compliance, in all material respects, with applicable environmental laws and regulations. Other Matters: The Company and its subsidiaries are parties to, or may be contingently liable in connection with other legal actions arising in the normal course of their businesses, the outcomes of which, in the opinion of management after consultation with counsel, would not have a material effect on the Company’s financial condition, results of operations, or cash flows.