CONDENSED CONSOLIDATED BALANCE SHEETS [Parenthetical] - USD ($) $ in Thousands |
Mar. 31, 2018 |
Dec. 31, 2017 |
|---|---|---|
| Trade accounts receivable, allowances | $ 9,866 | $ 11,019 |
| Allowance for Doubtful Other Receivables, Current | 227 | 227 |
| Inventories, reserves | 1,599 | 1,657 |
| Notes receivable, allowance | 598 | 759 |
| Property and equipment, accumulated depreciation | 167,306 | 164,720 |
| Amortizable intangible assets, accumulated amortization | $ 48,657 | $ 47,179 |
| Treasury stock, shares | 2,317,650 | 2,317,650 |
| Common Class A [Member] | ||
| Common stock, par value | $ 0.01 | $ 0.01 |
| Common stock, authorized | 80,000,000 | 80,000,000 |
| Common stock, issued | 22,940,576 | 22,932,451 |
| Common stock, outstanding | 20,622,926 | 20,614,801 |
| Common Class B [Member] | ||
| Common stock, par value | $ 0.01 | $ 0.01 |
| Common stock, authorized | 20,000,000 | 20,000,000 |
| Common stock, issued | 5,553,696 | 5,553,696 |
| Common stock, outstanding | 5,553,696 | 5,553,696 |
| X | ||||||||||
- Definition Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services. Reference 1: http://www.xbrl.org/2003/role/presentationRef
|
| X | ||||||||||
- Definition A valuation allowance for trade and other receivables due to an Entity within one year (or the normal operating cycle, whichever is longer) that are expected to be uncollectible. Reference 1: http://www.xbrl.org/2003/role/presentationRef
|
| X | ||||||||||
- Definition Amount of valuation allowance for receivables classified as other, due within one year or the normal operating cycle, if longer. No definition available.
|
| X | ||||||||||
- Definition A valuation allowance relating to a written agreement to receive money (at a specified future date(s) more than one year from the reporting date, consisting of principal as well as any accrued interest) for the portion that is expected to be uncollectible. Reference 1: http://www.xbrl.org/2003/role/presentationRef
|
| X | ||||||||||
- Definition Face amount or stated value per share of common stock. Reference 1: http://www.xbrl.org/2003/role/presentationRef
|
| X | ||||||||||
- Definition The maximum number of common shares permitted to be issued by an entity's charter and bylaws. Reference 1: http://www.xbrl.org/2003/role/presentationRef
|
| X | ||||||||||
- Definition Total number of common shares of an entity that have been sold or granted to shareholders (includes common shares that were issued, repurchased and remain in the treasury). These shares represent capital invested by the firm's shareholders and owners, and may be all or only a portion of the number of shares authorized. Shares issued include shares outstanding and shares held in the treasury. Reference 1: http://www.xbrl.org/2003/role/presentationRef
|
| X | ||||||||||
- Definition Number of shares of common stock outstanding. Common stock represent the ownership interest in a corporation. Reference 1: http://www.xbrl.org/2003/role/presentationRef
|
| X | ||||||||||
- Definition Accumulated amount of amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life. Reference 1: http://www.xbrl.org/2003/role/presentationRef
|
| X | ||||||||||
- Definition Amount of valuation reserve for inventory. Reference 1: http://www.xbrl.org/2003/role/presentationRef
|
| X | ||||||||||
- Definition Number of common and preferred shares that were previously issued and that were repurchased by the issuing entity and held in treasury on the financial statement date. This stock has no voting rights and receives no dividends. Reference 1: http://www.xbrl.org/2003/role/presentationRef
|
| X | ||||||||||
- Details
|
| X | ||||||||||
- Details
|