CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Allowances for trade accounts receivable	$ 10,884	$ 11,069
Preferred stock, shares authorized	30,000,000	30,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, shares authorized	300,000,000	300,000,000
Common stock, shares issued	99,193,000	100,944,000
Common stock, shares outstanding	99,193,000	100,944,000