Derivative Financial Instruments and Related Hedging Programs, Realized and Unrealized Gains (Losses) Table (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Summary Of Realized And Unrealized Gains (Losses)
Unrealized gains (losses)			$ 3.6	$ (2.3)
Not Designated as Hedging Instrument
Summary Of Realized And Unrealized Gains (Losses)
Realized (losses) gains	3.1	(2.3)	6.4	(4.8)
Unrealized gains (losses)	(1.3)	3.1	3.6	(2.3)
Operational Risk Hedges | Not Designated as Hedging Instrument
Summary Of Realized And Unrealized Gains (Losses)
Unrealized gains (losses)	(3.5)	1.5	0	(3.4)
Call Options | Not Designated as Hedging Instrument
Summary Of Realized And Unrealized Gains (Losses)
Unrealized gains (losses)	12.9	31.0	19.8	27.9
Bifurcated Conversion Feature | Not Designated as Hedging Instrument
Summary Of Realized And Unrealized Gains (Losses)
Unrealized gains (losses)	(10.7)	(29.4)	(16.2)	(26.8)
Aluminum | Not Designated as Hedging Instrument
Summary Of Realized And Unrealized Gains (Losses)
Realized (losses) gains	3.1	(2.0)	5.2	(3.6)
Aluminum | Operational Risk Hedges | Not Designated as Hedging Instrument
Summary Of Realized And Unrealized Gains (Losses)
Unrealized gains (losses)	(1.0)	1.7	1.3	(4.5)
Natural Gas | Not Designated as Hedging Instrument
Summary Of Realized And Unrealized Gains (Losses)
Realized (losses) gains	(0.1)	(0.5)	1.1	(1.3)
Natural Gas | Operational Risk Hedges | Not Designated as Hedging Instrument
Summary Of Realized And Unrealized Gains (Losses)
Unrealized gains (losses)	(1.6)	0	(1.0)	0.8
Electricity | Not Designated as Hedging Instrument
Summary Of Realized And Unrealized Gains (Losses)
Realized (losses) gains	0.1	0.3	0.1	0.2
Electricity | Operational Risk Hedges | Not Designated as Hedging Instrument
Summary Of Realized And Unrealized Gains (Losses)
Unrealized gains (losses)	(1.0)	(0.3)	(0.3)	0.3
Foreign Currency | Not Designated as Hedging Instrument
Summary Of Realized And Unrealized Gains (Losses)
Realized (losses) gains	0	(0.1)	0	(0.1)
Foreign Currency | Operational Risk Hedges | Not Designated as Hedging Instrument
Summary Of Realized And Unrealized Gains (Losses)
Unrealized gains (losses)	$ 0.1	$ 0.1	$ 0	$ 0