Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Statement of Financial Position [Abstract]
Accounts receivable, accumulated provision for doubtful accounts	$ 3,619	$ 3,018
Common stock, par value (in dollars per share)	$ 0	$ 0
Common stock, authorized shares (in shares)	320,000,000	320,000,000
Common stock, shares issued (in shares)	177,897,000	158,347,000
Treasury stock, shares at cost (in shares)	5,150,000	5,793,000
Treasury stock, shares held in rabbi trust	226,000	292,000