Consolidated Statements of Comprehensive Income (Parenthetical) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Consolidated Statements of Comprehensive Income
Net loss, tax benefits	$ 4.1	$ 2.7	$ 3.3
Amortization of prior service cost included in net periodic pension cost, tax expense		0.1	0.1
Amortization of net losses included in net periodic pension cost, tax expense	0.2	1.0	0.9
Reduction in obligation related to pension curtailment, tax expense		$ 5.4