CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $) In Millions, except Share data in Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
CONDENSED CONSOLIDATED BALANCE SHEETS
Allowances for doubtful accounts	$ 5.1	$ 6.9
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized	500,000	500,000
Common stock, shares issued	88,561	87,545
Convertible preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Convertible preferred stock, shares authorized	50,000	50,000
Convertible preferred stock, shares outstanding	0	0
Treasury stock, shares	22,425	20,724