CONSOLIDATED STATEMENTS OF Financial Position (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016
Trade accounts receivable, allowances	$ 1,937	$ 1,884	$ 2,224
Treasury stock, shares	85,000	83,000	83,000
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	38,580,000	37,701,000	38,283,000
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	24,932,000	24,221,000	24,245,000