Income Taxes Income Taxes (Unrecognized Tax Benefits) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Income Tax Disclosure [Abstract]
Unrecognized tax benefits — at beginning of year	$ 12.5	$ 10.8
Gross increases — tax positions of prior periods	12.2	0
Gross increases — current-period tax positions	2.3	2.8
Gross decreases — tax positions of prior periods	(6.0)	(0.8)
Gross decreases — settlements	0	(0.3)
Unrecognized tax benefits — at end of year	$ 21.0	$ 12.5