CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Statement of Financial Position [Abstract]
Receivables, allowance for doubtful accounts	$ 43,022	$ 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	178,494,000	178,621,000
Common stock, shares outstanding	145,833,000	146,458,000
Treasury stock, shares	32,661,000	32,163,000