CONDENSED CONSOLIDATED STATEMENTS OF FINANCIAL POSITION (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019
Trade accounts receivable, allowances	$ 1,887	$ 1,949	$ 1,696
Treasury stock, shares	93,000	90,000	90,000
Common Stock
Common stock, par value (in dollars per share)	$ 0.6944	$ 0.6944	$ 0.6944
Common stock, shares authorized	120,000,000	120,000,000	120,000,000
Common stock, shares issued	39,769,000	38,836,000	39,418,000
Class B Common Stock
Common stock, par value (in dollars per share)	$ 0.6944	$ 0.6944	$ 0.6944
Common stock, shares authorized	40,000,000	40,000,000	40,000,000
Common stock, shares issued	27,037,000	26,287,000	26,342,000