Valuation and Qualifying Account (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Allowance for Doubtful Accounts [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at the beginning of year	$ 9.5	$ 10.1	$ 9.1
Charged to (reversed from) costs and expenses	0.1	(0.2)	1.2
Write-offs, net of recoveries	(0.1)	(0.4)	(0.2)
Balance at the end of year	9.5	9.5	10.1
Sales Returns Reserve [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at the beginning of year	52.0	52.8	45.6
Charged as a reduction in revenues	35.9	46.3	42.6
Recoveries	(35.2)	(47.1)	(35.4)
Balance at the end of year	$ 52.7	$ 52.0	$ 52.8