CONDENSED CONSOLIDATED STATEMENTS OF FINANCIAL POSITION (Parenthetical) - USD ($) shares in Thousands, $ in Thousands	Sep. 30, 2020	Dec. 31, 2019	Sep. 30, 2019
Trade accounts receivable, allowances	$ 2,260	$ 1,949	$ 2,728
Treasury stock, shares	93	90	90
Common Stock
Common stock, par value (in dollars per share)	$ 0.6944	$ 0.6944	$ 0.6944
Common stock, shares authorized	120,000	120,000	120,000
Common stock, shares issued	39,336	38,836	39,019
Class B Common Stock
Common stock, par value (in dollars per share)	$ 0.6944	$ 0.6944	$ 0.6944
Common stock, shares authorized	40,000	40,000	40,000
Common stock, shares issued	27,025	26,287	26,300