Summary of Significant Accounting Policies (Policies)	12 Months Ended
Summary of Significant Accounting Policies (Policies)	Dec. 31, 2015
Accounting Policies [Abstract]
General	GENERAL We are primarily engaged in activities associated with timberland management, including the sale of timber, the management of approximately 1.6 million acres of timberlands and the purchase and sale of timberlands. We are also engaged in the manufacture and sale of wood products. Our timberlands and all of our wood products facilities are located within the continental United States. The primary market for our products is the United States. We converted to a Real Estate Investment Trust (REIT) effective January 1, 2006.
Consolidation	CONSOLIDATION The Consolidated Financial Statements include the accounts of Potlatch Corporation and its subsidiaries after elimination of significant intercompany transactions and accounts. There are no unconsolidated subsidiaries.
Significant Estimates	SIGNIFICANT ESTIMATES The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America, which we refer to in this report as U.S. GAAP, requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates and assumptions. Significant estimates are described in further detail below. Significant estimates include timber volumes, assumptions utilized for asset and disposal group impairment tests, income projections and tax planning strategies used to support realization of deferred tax assets, environmental liabilities, pension and postretirement obligation assumptions and fair value of derivative instruments.
Short Term Investments	SHORT-TERM INVESTMENTS Short-term investments consist of diversified depository accounts, money market funds and variable rate demand obligations, all of which have very short maturity periods and therefore earn an interest rate commensurate with low-risk instruments. We classify our short-term investments as "available for sale." There is no significant difference between cost and fair value. All short-term investments of REIT funds are made in compliance with the requirements of the Internal Revenue Code with respect to qualifying REIT investments.
Inventories	INVENTORIES Inventories are stated at the lower of cost or market. The last-in, first-out method is used to determine cost of logs, lumber and plywood for most of our operations. The average cost method is used to determine the cost of all other inventories. Expenses associated with idle capacity or other curtailments of production are reflected in cost of goods sold in the periods incurred.
Property, Plant and Equipment	PROPERTY, PLANT AND EQUIPMENT Property, plant and equipment are valued at cost less accumulated depreciation. Depreciation of buildings, equipment and other depreciable assets is determined using the straight-line method of depreciation. Estimated useful lives range from 30 to 40 years for buildings and structures and 2 to 25 years for equipment. Major improvements and replacements of property are capitalized. Maintenance, repairs and minor improvements and replacements are expensed. Upon retirement or other disposition of property, applicable cost and accumulated depreciation or amortization are removed from the accounts. Any gains or losses are included in earnings.
Timber and Timberland	TIMBER AND TIMBERLANDS Timber and timberlands are valued at cost less accumulated depletion and amortization. For fee timber, the capitalized cost includes costs related to stand establishment, including costs of preparing the land for planting, cost of seeds or seedlings and tree planting, including labor, materials, depreciation of company-owned equipment and the cost of contract services. Upon completion of planting activities and field inspection to assure the planting operation was successful, a plantation will be considered “established.” Subsequent expenditures made to maintain the integrity or enhance the growth of an established plantation or stand are expensed. Post-establishment expenses include release spray treatments, pest control activities, thinning operations, fertilization and replanting seedlings lost through mortality. Expenditures for forest management consist of regularly recurring items necessary for ownership and administration of timber producing property such as fire protection, property taxes and insurance, silviculture costs incurred subsequent to stand establishment, cruising (physical inventory), property maintenance and salaries, supplies, travel, record-keeping and other normal recurring administrative personnel costs. These expenditures are accounted for as current operating expenses. Timberland acquisitions are capitalized and the cost is allocated to timberland, merchantable sawlogs, merchantable pulpwood, reproduction (young growth not yet merchantable), logging roads and other land improvements, generally based on relative appraised values. The aggregate estimated volume of current standing merchantable timber inventory is updated at least annually to reflect increases due to reclassification of young growth to merchantable timber when the young growth meets defined diameter specifications, the annual growth of merchantable timber and the acquisition of additional merchantable timber and to reflect decreases due to timber harvests and land sales. Timber volumes are estimated from cruises of the timber tracts, which are completed on our timberlands on approximately a five to ten year cycle. Since the individual cruises collect field data at different times for specific sites, the growth model projects standing inventory from the cruise date to a common reporting date. Annual growth rates for the merchantable inventory have historically been in the range of 2%-5% in the North and 6%-9% in the South. Depletion represents the amount charged to expense as fee timber is harvested. Rates at which timber is depleted are calculated annually for each of our depletion pools by dividing the beginning of year balance of the merchantable timber accounts by the forest inventory volume, after inventory updates for growth projection adjustments and new timber cruises. The base cost of logging roads, such as the clearing, grading, and ditching, is not amortized and remains a capitalized item until obliteration or other disposition. Other portions of the initial logging road cost, such as bridges, culverts and gravel surfacing are amortized over their useful lives, which range from 5 to 20 years. Costs associated with temporary logging roads that will not remain part of our road system are expensed as incurred.
Real Estate Sales	REAL ESTATE SALES Sales of non-core timberland are considered to be part of our normal operations. We therefore classify revenue and costs associated with real estate sold in revenues and cost of goods sold, respectively, in our Consolidated Statements of Income. Cash generated from real estate sales is included as an operating activity in our Consolidated Statements of Cash Flows.
Like-Kind Exchange and Restricted Cash	LIKE-KIND EXCHANGES AND RESTRICTED CASH In order to acquire and sell assets, primarily timberlands, in a tax efficient manner, we sometimes enter into like-kind exchange (LKE) tax-deferred transactions. There are two main types of LKE transactions: forward transactions, in which property is sold and the proceeds are reinvested by acquiring similar property; and reverse transactions, in which property is acquired and similar property is subsequently sold by us. Both forward and reverse transactions must be completed within prescribed time periods under Internal Revenue Code section 1031. We use a qualified intermediary to facilitate LKE transactions. Proceeds from forward transactions are held by the intermediary and are classified as restricted cash within non-current other assets, because we intend to reinvest the funds in similar properties. If the acquisition of suitable LKE properties is not completed within 180 days of the sale of the company-owned property, the proceeds are distributed to us by the intermediary and are reclassified as available cash and applicable income taxes are determined. In the case of reverse transactions in which we have not yet completed LKE sales of company-owned land to match with property purchased on our behalf by the intermediary, the amount associated with the property purchased on our behalf but not yet matched with LKE sales is classified as a non-current asset and included in “Timber and timberlands, net” in our Consolidated Balance Sheets and as “Acquisition of timber and timberlands” in the investing activities section of our Consolidated Statements of Cash Flows.
Long-Lived Assets	LONG-LIVED ASSETS Our long-lived assets are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable, as measured by its undiscounted estimated future cash flows. We use our operational budgets to estimate future cash flows. The estimates are adjusted periodically to reflect changing business conditions. Impaired assets are written down to fair value. Assets to be disposed of are reported at the lower of carrying amount or fair value less cost to sell. We recognize a liability and an asset equal to the fair value of our legal obligations to perform asset retirement activities if the amount can be reasonably estimated. We review these obligations annually and do not expect them to have a material effect on our financial position, results of operations or cash flows.
Income Taxes	INCOME TAXES We use the asset and liability method of accounting for income taxes. Under this method, deferred tax assets and liabilities are recognized for the estimated future tax consequences attributable to differences between the financial statement carrying amounts of assets and liabilities and their respective tax bases, operating loss carryforwards and tax credit carryforwards. Deferred tax assets and liabilities are measured pursuant to tax laws using rates expected to apply to taxable income in the years in which the temporary differences are expected to be recovered or settled. We recognize the effect of a change in income tax rates on deferred tax assets and liabilities in the Consolidated Statements of Income and Consolidated Statements of Comprehensive Income in the period that includes the enactment date of the rate change. We record a valuation allowance to reduce the carrying amounts of deferred tax assets if it is more likely than not that such deferred tax assets will not be realized.
Revenue Recognition	REVENUE RECOGNITION We recognize revenue from the sale of timber when risk of loss transfers to the buyer and the quantity sold is determinable. These sales take the form of delivered logs, pay-as-cut contracts, timber deeds and lump sum contracts. On delivered log sales, revenue includes amounts billed for logging and hauling and is recognized at the point the logs are delivered and scaled. Revenue is recognized on timber deeds and lump sum contracts generally upon closing or when the contracts are effective, which is the point at which the buyer assumes risk of loss associated with the standing timber. We receive cash consideration in full and recognize revenue at closing on substantially all our real estate sales. We recognize revenue from the sale of manufactured wood products and residual by-products when there is persuasive evidence of a sales agreement, the price to the customer is fixed and determinable, collection is reasonably assured, and title and the risk of loss passes to the customer. Shipping terms generally indicate when title and the risk of loss have passed. Revenue is recognized at shipment for sales when shipping terms are FOB (free on board) shipping point. For sales where shipping terms are FOB destination, revenue is recognized when the goods are received by the customer. Revenue is recognized net of any sales taxes collected. Sales taxes, when collected, are recorded as a current liability and remitted to the appropriate governmental entities. Costs for shipping and handling are included in cost of goods sold in our Consolidated Statements of Income.
Equity-Based Compensation	EQUITY-BASED COMPENSATION Equity-based awards are measured at fair value on the dates they are granted or modified. These measurements establish the cost of the equity-based awards for accounting purposes. The cost of the equity-based award is then recognized in the Consolidated Statements of Income over each employee’s required service period. See Note 12: Equity-Based Compensation Plans for more information about our equity-based compensation.
New Accounting Pronouncements	NEW ACCOUNTING PRONOUNCEMENTS In May 2014, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2014-09, Revenue from Contracts with Customers: Topic 606 (ASU 2014-09), which requires an entity to recognize revenue when promised goods or services are transferred to customers in an amount that reflects the consideration that is expected to be received for those goods or services. The guidance permits either a retrospective application of the new standard with restatement of prior years or prospective application of the new standard with disclosure of results under old standards. In August 2015, the FASB issued ASU 2015-14, Revenue from Contracts with Customers (Topic 606) - Deferral of the Effective Date, which deferred the effective date of ASU No. 2014-09 by one year. Therefore, ASU No. 2014-09 is effective for us on January 1, 2018. The adoption of this guidance is not expected to have a significant effect on our consolidated financial statements. In April 2015, the FASB issued ASU No. 2015-03, Interest - Imputation of Interest, Simplifying the Presentation of Debt Issuance Costs. The amendments in ASU No. 2015-03 require that debt issuance cost related to a recognized debt liability be presented in the balance sheet as a direct deduction from the carrying amount of that debt. In August, the FASB issued ASU No. 2015-15, Interest-Imputation of Interest (Subtopic 835-30) Presentation and Subsequent Measurement of Debt Issuance Costs Associated with Line-of-Credit Arrangements, Amendments to SEC Paragraphs Pursuant to Staff Announcement at June 18, 2015 EITF Meeting, which clarified that debt issuance costs related to a line-of-credit arrangement may be deferred and presented as an asset and subsequently amortized ratably over the term of the line-of-credit arrangement, regardless of whether there is any outstanding borrowings on the line-of-credit arrangement. ASU No. 2015-03 is effective for us January 1, 2016, with early adoption permitted. We have adopted ASU No. 2015-03 and ASU No. 2015-15 on a retrospective basis as of and for the year-ended December 31, 2015. To conform to this new presentation, debt issuance costs of $3.7 million at December 31, 2014 have been reclassed from other current assets and other long-term assets to long-term debt. In May 2015, the FASB issued ASU No. 2015-07, Disclosures for Investments in Certain Entities that Calculate Net Asset Value per Share (or Its Equivalent), which removes the requirement to categorize within the fair value hierarchy investments for which fair value is measured using the net asset value per share practical expedient and, instead, permits separate disclosure. This ASU is effective for us on January 1, 2016 and will impact disclosure of investments in certain pension assets in Note 11: Savings Plans, Pension Plans and Other Postretirement Employee Benefits. In July 2015, the FASB issued ASU No. 2015-11, Inventory (Topic 330) - Simplifying the Measurement of Inventory. The amendments in ASU No. 2015-11 apply to inventory measured using first-in, first-out (FIFO) or average cost and will require entities to measure inventory at the lower of cost or net realizable value. Net realizable value is the estimated selling price in the normal course of business, minus the cost of completion, disposal and transportation. Replacement cost and net realizable value less a normal profit margin will no longer be considered. ASU No. 2015-11 is effective for us on January 1, 2017, with early adoption permitted. We adopted ASU No. 2015-11 as of October 1, 2015 with no impact on our consolidated financial statements. In November 2015, the FASB issued ASU No. 2015-17, Income Taxes (Topic 740), which requires deferred tax assets and liabilities to be classified as noncurrent on the balance sheet. ASU No. 2015-17 may be applied either prospectively to all deferred tax assets and liabilities or retrospectively to all periods presented. ASU No. 2015-17 is effective for us on January 1, 2017 with early application permitted. We have adopted ASU No. 2015-17 prospectively as of December 31, 2015. As allowed by the guidance, prior periods have not been reclassified.