BASIS OF PRESENTATION (Policies)	9 Months Ended
Sep. 30, 2021
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Consolidation	Our consolidated financial statements provide an overall view of our results of operations, financial condition and cash flows. They include our accounts and the accounts of entities we control, including majority-owned domestic and foreign subsidiaries. They do not include our intercompany transactions and accounts, which are eliminated. Throughout these Notes to Consolidated Financial Statements, unless specified otherwise, references to “Weyerhaeuser,” “we,” “the company” and “our” refer to the consolidated company.
Earnings Per Share	We use the treasury stock method to calculate the dilutive effect of our outstanding stock options, restricted stock units and performance share units.
Fair Value of Financial Instruments	To estimate the fair value of fixed rate long-term debt, we used the market approach, which is based on quoted market prices we received for the same types and issues of our debt. We believe that our variable rate long-term debt and line of credit instruments have net carrying values that approximate their fair values with only insignificant differences. The inputs to these valuations are based on market data obtained from independent sources or information derived principally from observable market data. The difference between the fair value and the carrying value represents the theoretical net premium or discount we would pay or receive to retire all debt at the measurement date.

Disclosure of accounting policy regarding (1) the principles it follows in consolidating or combining the separate financial statements, including the principles followed in determining the inclusion or exclusion of subsidiaries or other entities in the consolidated or combined financial statements and (2) its treatment of interests (for example, common stock, a partnership interest or other means of exerting influence) in other entities, for example consolidation or use of the equity or cost methods of accounting. The accounting policy may also address the accounting treatment for intercompany accounts and transactions, noncontrolling interest, and the income statement treatment in consolidation for issuances of stock by a subsidiary.

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Disclosure of accounting policy for computing basic and diluted earnings or loss per share for each class of common stock and participating security. Addresses all significant policy factors, including any antidilutive items that have been excluded from the computation and takes into account stock dividends, splits and reverse splits that occur after the balance sheet date of the latest reporting period but before the issuance of the financial statements.

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Disclosure of accounting policy for determining the fair value of financial instruments.

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