CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Statement of Financial Position [Abstract]
Receivables, allowance for doubtful accounts	$ 39,802	$ 43,455
Preferred stock, par value (in dollars per share)	$ 0.10	$ 0.10
Preferred stock, shares authorized (shares)	20,000,000	20,000,000
Preferred stock, shares issued (shares)	0	0
Preferred stock, shares outstanding (shares)	0	0
Common stock, par value (in dollars per share)	$ 0.10	$ 0.10
Common stock, shares authorized (shares)	480,000,000	480,000,000
Common stock, shares issued (shares)	178,783,000	178,784,000
Common stock shares outstanding (shares)	141,898,000	143,455,000
Treasury stock (shares)	36,885,000	35,329,000