Recently Adopted Accounting Standards (Policies)	6 Months Ended
Recently Adopted Accounting Standards (Policies)	Jun. 30, 2018
Accounting Changes and Error Corrections [Abstract]
Inventories	The Corporation values its inventory at the lower of cost or net realizable value with approximately 86 percent valued by the last-in, first-out ("LIFO") costing method.
Goodwill and Other Intangible Assets	The Corporation evaluates its goodwill and indefinite-lived intangible assets for impairment on an annual basis during the fourth quarter or whenever indicators of impairment exist.
Product Warranties	The Corporation issues certain warranty policies on its office furniture and hearth products that provide for repair or replacement of any covered product or component that fails during normal use because of a defect in design, materials, or workmanship. Allowances have been established for the anticipated future costs associated with the Corporation's warranty programs. A warranty allowance is determined by recording a specific allowance for known warranty issues and an additional allowance for unknown claims expected to be incurred based on historical claims experience. Actual claims incurred could differ from the original estimates, requiring adjustments to the allowance.
Fair Value Measurements	For recognition purposes, on a recurring basis, the Corporation is required to measure at fair value its marketable securities, derivative financial instruments, variable-rate and fixed-rate debt obligations, and deferred stock-based compensation. The marketable securities are comprised of money market funds, government securities, and corporate bonds. When available, the Corporation uses quoted market prices to determine fair value and classifies such measurements within Level 1. Where market prices are not available, the Corporation makes use of observable market-based inputs (prices or quotes from published exchanges and indexes) to calculate fair value using the market approach, in which case the measurements are classified within Level 2.
Share-based Compensation, Option and Incentive Plans	The Corporation measures stock-based compensation expense at grant date, based on the fair value of the award, and recognizes expense over the employees' requisite service periods. Stock-based compensation expense is the cost of stock options and time-based restricted stock units issued under the approved stock-based compensation plans and shares issued under the approved member stock purchase plans.
Recently Adopted Accounting Standards	In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606). The new standard replaces most existing revenue recognition guidance in U.S. GAAP. The core principle of the ASU requires companies to reevaluate when revenue is recorded on a transaction based upon newly defined criteria, either at a point in time or over time as goods or services are delivered. The ASU requires additional disclosure about the nature, amount, timing, and uncertainty of revenue and cash flows arising from customer contracts, including significant judgments and estimates, and changes in those estimates. The FASB has issued ASU No. 2016-08, Revenue from Contracts with Customers: Principal versus Agent Considerations, ASU No. 2016-10, Revenue from Contracts with Customers: Identifying Performance Obligations and Licensing, and ASU No. 2016-12, Revenue from Contracts with Customers: Narrow Scope Improvements and Practical Expedients to provide further clarification and guidance. The Corporation implemented the new standard in the first quarter of fiscal 2018 using the modified-retrospective method, which required the new guidance to be applied prospectively to revenue transactions completed on or after the effective date. Given the nature of the Corporation's revenue transactions, the new guidance did not have a material impact on the Corporation's results of operations or financial position. All necessary changes required by the new standard, including those to the Corporation's accounting policies, controls, and disclosures, have been identified and implemented as of the beginning of fiscal 2018. See "Note 2. Revenue from Contracts with Customers" in the Notes to Condensed Consolidated Financial Statements for further information. In August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows - Classification of Certain Cash Receipts and Cash Payments. The new standard provides classification guidance on eight cash flow issues including debt prepayment, settlement of zero-coupon bonds, contingent consideration payments made after a business combination, proceeds from the settlements of insurance claims, proceeds from the settlement of corporate-owned life insurance policies, and distributions received from equity method investees. The Corporation implemented the new standard in the first quarter of fiscal 2018. This standard did not have a material effect on the condensed consolidated financial statements or related disclosures. In October 2016, the FASB issued ASU No. 2016-16, Intra-Entity Transfers of Assets Other Than Inventory. The new standard requires an entity to recognize the income tax consequences of intra-entity transfers of assets other than inventory when the transfer occurs. The Corporation implemented the new standard in the first quarter of fiscal 2018. This standard did not have a material effect on the condensed consolidated financial statements or related disclosures. In March 2017, the FASB issued ASU No. 2017-07, Improving the Presentation of Net Periodic Pension Cost and Net Periodic Post-retirement Benefit Cost. The new standard requires an entity with defined benefit and post-retirement benefit plans to present the service cost component of the net periodic benefit cost in the same income statement line item or items as other compensation costs arising from services rendered by employees during the period. All other components of net periodic benefit cost will be presented outside of operating income, if a subtotal is presented. The Corporation implemented the new standard in the first quarter of fiscal 2018 and it was applied retrospectively to each period presented. This standard did not have a material effect on the condensed consolidated financial statements or related disclosures.
Business Segment Information	Management views the Corporation as being in two reportable segments based on industries: office furniture and hearth products, with the former being the principal segment. The aggregated office furniture segment manufactures and markets a broad line of commercial and home office furniture which includes storage products, desks, credenzas, chairs, tables, bookcases, freestanding office partitions and panel systems, and other related products. The hearth products segment manufactures and markets a broad line of gas, electric, wood, and biomass burning fireplaces, inserts, stoves, facings, and accessories, principally for the home. For purposes of segment reporting, intercompany sales between segments are not material, and operating profit is income before income taxes exclusive of certain unallocated general corporate expenses. These unallocated general corporate expenses include the net costs of the Corporation's corporate operations. Management views interest income and expense as corporate financing costs and not as a reportable segment cost. In addition, management applies an effective income tax rate to its consolidated income before income taxes so income taxes are not reported or viewed internally on a segment basis. Identifiable assets by segment are those assets applicable to the respective industry segments. Corporate assets consist principally of cash and cash equivalents, short-term investments, long-term investments, IT infrastructure, and corporate office real estate and related equipment. No geographic information for revenues from external customers or for long-lived assets is disclosed since the Corporation's primary market and capital investments are concentrated in the United States.