CONSOLIDATED STATEMENTS OF FINANCIAL POSITION (Parenthetical) - USD ($) shares in Thousands, $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Trade accounts receivable, allowances	$ 1,694	$ 1,949
Treasury stock, shares	93	90
Common Stock
Common stock, par value (in dollars per share)	$ 0.6944	$ 0.6944
Common stock, shares authorized	120,000	120,000
Common stock, shares issued	39,073	38,836
Class B Common Stock
Common stock, par value (in dollars per share)	$ 0.6944	$ 0.6944
Common stock, shares authorized	40,000	40,000
Common stock, shares issued	27,012	26,287