CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
CONDENSED CONSOLIDATED BALANCE SHEETS
Trade accounts receivable, allowance for doubtful accounts (in dollars)	$ 2,159	$ 1,297
Common stock, par value (in dollars per share)	$ (0.01)	$ (0.01)
Common stock, shares authorized	175,772,173	175,772,173
Common stock, shares issued	158,210,719	158,210,719
Common stock held in treasury, at cost	2,106,865	2,448,553