Income Taxes Income Taxes (Unrecognized Tax Benefits) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Income Tax Disclosure [Abstract]
Unrecognized tax benefits — at beginning of year	$ 10.8	$ 7.0
Gross increases — tax positions of prior periods	0	1.5
Gross increases — current-period tax positions	2.8	2.3
Gross decreases — tax positions of prior periods	(0.8)	0
Gross decreases — settlements	(0.3)	0
Unrecognized tax benefits — at end of year	$ 12.5	$ 10.8