CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Statement of Financial Position [Abstract]
Receivables, allowance for doubtful accounts	$ 45,952	$ 41,051
Preferred stock, par value	$ 0.10	$ 0.10
Preferred stock, shares authorized	20,000,000	20,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.10	$ 0.10
Common stock, shares authorized	480,000,000	480,000,000
Common stock, shares issued	178,510,000	178,621,000
Common stock, shares outstanding	144,108,000	146,458,000
Treasury stock, shares	34,402,000	32,163,000