Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Statement of Financial Position [Abstract]
Trade Accounts receivable, allowances	$ 4,073	$ 4,975
Common Stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	200,000,000	200,000,000
Common Stock shares issued	87,556,248	87,556,248
Common Stock, shares outstanding	55,051,158	60,392,905
Treasury stock, shares	32,505,090	27,163,343