CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $) In Thousands, except Per Share data, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 245,975	$ 235,747
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	600,000	600,000
Common stock, shares, issued	215,358	215,075
Treasury stock, shares	63,538	56,744