Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) shares in Thousands, $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Statement of Financial Position [Abstract]
Accounts receivable, accumulated provision for doubtful accounts	$ 3,658	$ 5,311
Common stock, par value (in dollars per share)	$ 0	$ 0
Common stock, authorized shares	320,000	320,000
Common stock, shares issued	175,347	175,384
Treasury stock, shares at cost	22,943	23,788