Background and Basis of Presentation	12 Months Ended
Background and Basis of Presentation	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Background and Basis of Presentation	Background and Basis of Presentation Description of Business: Alexander & Baldwin, Inc. ("A&B" or the "Company") is a real estate investment trust ("REIT") headquartered in Honolulu, Hawai‘i. The Company operates in three segments: Commercial Real Estate; Land Operations; and Materials & Construction. A description of each of the Company's reporting segments is as follows: •Commercial Real Estate ("CRE") - This segment functions as a vertically integrated real estate investment company with core competencies in investments and acquisitions (i.e., identifying opportunities and acquiring properties); construction and development (i.e., designing and ground-up development of new properties or repositioning and redevelopment of existing properties); and in-house leasing and property management (i.e., executing new and renegotiating renewal lease arrangements, managing its properties' day-to-day operations and maintaining positive tenant relationships). The Company's preferred asset classes include improved properties in retail and industrial spaces and also urban ground leases. Its focus within improved retail properties, in particular, is on grocery-anchored neighborhood shopping centers that meet the daily needs of Hawai‘i citizens. Through its core competencies and with its experience and relationships in Hawai‘i, the Company seeks to create special places that enhance the lives of Hawai‘i residents and to provide venues and opportunities that enable its tenants to thrive. Income from this segment is principally generated by owning, operating and leasing real estate assets. •Land Operations - This segment includes the Company's legacy assets and landholdings that are subject to the Company's simplification and monetization effort. Financial results from this segment are principally derived from real estate development and land sales, income/loss from real estate joint ventures, hydroelectric energy and other legacy business activities. •Materials & Construction ("M&C") - This segment operates as Hawai‘i's largest asphalt paving contractor and is one of the state's largest natural materials and infrastructure construction companies. Such activities are primarily conducted through its wholly-owned subsidiary, Grace Pacific LLC ("Grace Pacific"), a materials and construction company in Hawai‘i. Grace Pacific owns hot-mix asphalt plants throughout the state that support its internal paving operations and third-party customers. Grace Pacific also owns and operates a rock quarry and processing plant in Makakilo, Hawai‘i. In addition, Grace Pacific offers a variety of related for-sale and for-rent services including temporary and permanent roadway traffic control (GP Roadway Solutions, Inc. or "GPRS") and other related products and services. Grace Pacific also holds a 50% interest in an unconsolidated affiliate, Maui Paving, LLC ("Maui Paving"), which operates primarily on the island of Maui. Additional activity in the M&C segment includes its share of the results of operations of an unconsolidated investment, Pohaku Pa‘a LLC ("Pohaku"). Pohaku, through its wholly-owned subsidiaries, operates rock quarries on the islands of Oahu and Maui and sells a wide range of products that include ready-mix concrete, rock and sand aggregates and cultured stone and related products. As of December 31, 2020, the Company owns a portfolio of commercial real estate improved properties in Hawai‘i consisting of 22 retail centers, ten industrial assets and four office properties, representing a total of 3.9 million square feet of gross leasable area; it also owns a portfolio of ground leases in Hawai‘i representing 153.8 acres as of December 31, 2020. Basis of Presentation and Principles of Consolidation: The Company presents its financial statements in accordance with accounting principles generally accepted in the United States ("GAAP") as outlined in the Financial Accounting Standard Board ("FASB") Accounting Standards Codification (the "Codification" or "ASC"). The Codification is the single source of authoritative accounting principles applied by nongovernmental entities in the preparation of financial statements in conformity with GAAP. The consolidated financial statements include the accounts of the Company (including all wholly-owned subsidiaries), as well as all other entities in which the Company has a controlling financial interest. Intercompany transactions and balances have been eliminated in consolidation. Significant investments in businesses, partnerships and limited liability companies in which the Company does not have a controlling financial interest, but the Company has the ability to exercise significant influence, are accounted for using the equity method. A controlling financial interest in an entity may be established (i) through the Company holding a majority voting interest or (ii) if the Company is the primary beneficiary of an entity that qualifies as a variable interest entity ("VIE"), as defined in the Codification. The Company evaluates all partnerships, joint ventures and other arrangements with variable interests to determine if the entity or arrangement qualifies as a VIE. VIEs are entities where investors lack sufficient equity at risk for the entity to finance its activities without additional subordinated financial support or where equity investors, as a group, lack one of the following characteristics: (a) the power to direct the activities that most significantly impact the entity’s economic performance, (b) the obligation to absorb the expected losses of the entity, or (c) the right to receive the expected returns of the entity. If the entity or arrangement qualifies as a VIE and the Company is determined to be the primary beneficiary, the Company is required to consolidate the assets, liabilities, and results of operations of the VIE. The Company reevaluates whether an entity is a VIE as needed (i.e., when assessing reconsideration events that result in changes in the factors mentioned above) as part of determining if the consolidation or equity method treatment remains appropriate. As of December 31, 2020, the Company had an interest in various unconsolidated joint ventures that the Company accounts for using the equity method. Other than the obligations described in Note 12, obligations of the Company's joint ventures do not have recourse to the Company and the Company's maximum exposure is limited to its investment. The consolidated financial statements include the historical results of GP/RM Prestress, LLC ("GPRM"), a supplier of structural precast/prestressed concrete products, which was owned 51% by the Company, through the date of its disposal during the year ended December 31, 2020 (refer to Note 24). The consolidated financial statements also include the results of GLP Asphalt, LLC ("GLP Asphalt"), an importer and distributor of liquid asphalt, which is owned 70% by the Company. These entities were consolidated because the Company held a controlling financial interest through its majority voting interest in the entities. The remaining interest in these entities is reported as Noncontrolling interest and Redeemable Noncontrolling Interest in the consolidated financial statements. Profits, losses and cash distributions are allocated in accordance with the respective operating agreements. Use of Estimates: The preparation of the consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported. Estimates and assumptions are used for, but not limited to: (i) asset impairments, including intangible assets and goodwill, (ii) litigation and contingencies, (iii) revenue recognition for long-term real estate developments and construction contracts, (iv) pension and postretirement estimates, and (v) income taxes. Future results could be materially affected if actual results differ from these estimates and assumptions. Customer Concentration: A significant portion of Materials & Construction revenue and accounts receivable is generated directly and indirectly from projects administered by the City and County of Honolulu and from the State of Hawai‘i. Reductions in funding of infrastructure projects by these government agencies could reduce revenue and profits from the M&C segment. Further, although the customer mix of real estate sales in our Land Operations segment may be diverse in any given period, during the years ended December 31, 2018 and December 31, 2019, the Land Operations segment recognized gross profits of $162.2 million and $6.7 million, respectively, in connection with the sale of approximately 41,000 acres of Maui agricultural land and 100% of the Company's ownership interest in Central Maui Feedstocks LLC and Kulolio Ranch LLC (collectively referred to as the "Agricultural Land Sale"). Rounding: Amounts in the consolidated financial statements and notes are rounded to the nearest tenth of a million. Accordingly, a recalculation of some per-share amounts and percentages, if based on the reported data, may result in differences. Reclassifications: Certain amounts presented in the prior year have been reclassified to conform to the current year presentation (e.g., captions previously presented in the prior years that, in the currently presented periods, are less than five percent of total assets or total liabilities were combined in the current year consolidated balance sheets). Also refer to Note 2 to the consolidated financial statements for such reclassifications made in conjunction with the adoption of recent accounting pronouncements. Further, a reclassification was made to the consolidated statements of cash flows to present, on a net basis, amounts previously presented separately within cash flows from operating activities (i.e., to present activity related to proceeds and expenditures of real estate development/other property for sale – normal operating activity in the Company's Land Operations segment – on a net basis similar to the presentation of changes in other inventories held by the Company). This change does not affect previously reported cash flows from operating activities in the consolidated statements of cash flows.