CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands |
Mar. 31, 2020 |
Dec. 31, 2019 |
|---|---|---|
| Trade accounts receivable, allowances | $ 11,408 | $ 10,947 |
| Inventories, reserves | 1,431 | 1,271 |
| Notes receivable, allowance | 930 | 954 |
| Property and equipment, accumulated depreciation | 175,212 | 173,122 |
| Amortizable intangible assets, accumulated amortization | $ 56,604 | $ 55,617 |
| 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 | 23,447,317 | 23,447,317 |
| Common stock, outstanding | 21,129,667 | 21,129,667 |
| 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://fasb.org/us-gaap/role/ref/legacyRef
|
| X | ||||||||||
- Definition Amount of allowance for credit loss on accounts receivable, classified as current. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
|
| X | ||||||||||
- Definition Amount of allowance for credit loss on financing receivable, classified as noncurrent. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
|
| X | ||||||||||
- Definition Face amount or stated value per share of common stock. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
|
| X | ||||||||||
- Definition The maximum number of common shares permitted to be issued by an entity's charter and bylaws. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
|
| 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://fasb.org/us-gaap/role/ref/legacyRef
|
| X | ||||||||||
- Definition Number of shares of common stock outstanding. Common stock represent the ownership interest in a corporation. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
|
| 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/disclosureRef
|
| X | ||||||||||
- Definition Amount of valuation reserve for inventory. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
|
| 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://fasb.org/us-gaap/role/ref/legacyRef
|
| X | ||||||||||
- Details
|
| X | ||||||||||
- Details
|