Accumulated Other Comprehensive Income (Loss) (Details 2) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Amount reclassified from AOCI, Derivatives	$ (4.3)	$ (0.6)	$ (5.5)	$ (3.5)
Amount reclassified from AOCI, Derivatives, Tax provision (benefit)	(1.7)		(2.1)
Amount reclassified from AOCI, Derivatives, Net of tax	(2.6)		(3.4)
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, before Reclassification Adjustments and Tax [Abstract]
Amount reclassified from AOCI, Postretirement benefit plans, Prior service (cost) credit	3.8	2.9	11.4	8.8
Amount reclassified from AOCI, Postretirement benefit plans, Actuarial costs	(33.5)	(29.9)	(100.5)	(89.8)
Amount reclassified from AOCI, Postretirement benefit plans, Total before tax	(29.7)		(89.1)
Amount reclassified from AOCI, Postretirement benefit plans, Tax provision (benefit)	(11.4)	(10.3)	(34.3)	(31.0)
Amount reclassified from AOCI, Postretirement benefit plans, Net of tax	(18.3)	(16.7)	(54.8)	(50.0)
Nickel and other raw material contracts
Amount reclassified from AOCI, Derivatives	(2.3)		(3.8)
Natural gas contracts
Amount reclassified from AOCI, Derivatives	(0.9)		(2.4)
Electricity contracts
Amount reclassified from AOCI, Derivatives	0		(0.3)
Foreign exchange contracts
Amount reclassified from AOCI, Derivatives	$ (1.1)		$ 1.0