Consolidated Statements of Comprehensive Income (Loss) Parenthetical (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Net gain (loss) arising from remeasurement during the period, tax	$ (30.7)	$ 5.1	$ 30.9
Net prior service credit, tax	(6.1)
Amortization of prior service benefits included in net income, tax	5.2	4.8	4.7
Amortization of net actuarial loss included in net income, tax	(10.1)	(9.5)	(7.6)
Reclassification adjustment for curtailment (gain) loss included in net income, tax	$ 0.2		$ (1.5)