Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Statement of Financial Position [Abstract]
Trade accounts receivable, allowance for doubtful accounts	$ 12,178	$ 12,619
Preferred stock, shares authorized	5,000,000	5,000,000
Common stock, shares authorized	400,000,000	400,000,000
Common stock, shares issued	290,149,384	295,867,844
Common stock, shares outstanding	290,149,384	295,867,844