Organization and Operations and Basis of Presentation	6 Months Ended
Organization and Operations and Basis of Presentation	Jun. 30, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Operations and Basis of Presentation	Organization and Operations and Basis of Presentation California Water Service Group (the Company) is a holding company that provides water utility and other related services in California, Washington, New Mexico, Hawaii, and Texas through its wholly-owned subsidiaries. California Water Service Company (Cal Water), Washington Water Service Company (Washington Water), New Mexico Water Service Company (New Mexico Water), Hawaii Water Service Company, Inc. (Hawaii Water), and TWSC, Inc. (Texas Water) provide regulated utility services under the rules and regulations of their respective state’s regulatory commissions (jointly referred to herein as the Commissions). CWS Utility Services and HWS Utility Services LLC provide non-regulated water utility and utility-related services. The Company operates in one reportable segment, providing water and related utility services. Basis of Presentation The unaudited condensed consolidated interim financial information has been prepared in accordance with accounting principles generally accepted in the United States of America (GAAP) for interim financial information and in accordance with the instructions to Form 10-Q and Rule 10-01 of Regulation S-X promulgated by the Securities and Exchange Commission (SEC) and therefore do not contain all of the information and footnotes required by GAAP and the SEC for annual financial statements. The unaudited condensed consolidated financial statements should be read in conjunction with the Company’s consolidated financial statements included in its Annual Report on Form 10-K for the year ended December 31, 2020 as filed with the SEC on February 25, 2021. The preparation of the Company’s unaudited condensed consolidated interim financial statements in accordance with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the balance sheet dates and the reported amounts of revenues and expenses for the periods presented. These include, but are not limited to, estimates and assumptions used in determining the Company’s regulatory asset and liability balances based upon probability assessments of regulatory recovery, revenues earned but not yet billed, asset retirement obligations, allowance for credit losses, pension and other employee benefit plan liabilities, and income tax-related assets and liabilities. Actual results could differ from these estimates. In the opinion of management, the accompanying unaudited condensed consolidated interim financial statements reflect all adjustments, consisting of normal recurring transactions that are necessary to provide a fair presentation of the results for the periods covered. Due to the seasonal nature of the water business, the results for interim periods are not indicative of the results for a 12-month period. Revenue and income are generally higher in the warm, dry summer months when water usage and sales are greater. Revenue and income are generally lower in the winter months when cooler temperatures and rainfall curtail water usage and sales. Noncontrolling Interests Noncontrolling interests in the Company’s condensed consolidated financial statements represents the 38.87% interest not owned by Texas Water in a consolidated subsidiary. Texas Water obtained control over the subsidiary on May 1, 2021. Since the Company controls this subsidiary, its financial statements are consolidated with those of the Company, and the noncontrolling owner’s 38.87% share of the subsidiary’s net assets and results of operations is deducted and reported as noncontrolling interests on the condensed consolidated balance sheet and as net loss attributable to noncontrolling interests in the condensed consolidated statement of operations.