Stock-Based Compensation (Tables)

6 Months Ended

Jun. 30, 2012

Stock-Based Compensation [Abstract]

Net stock-based compensation expense

	For the Three Months Ended June 30,				For the Six Months Ended June 30,
	2012		2011		2012		2011
Net stock-based compensation expense	$	4.5	$	4.2	$	8.3	$	9.1