Commitments and Contingencies Obligation Reserves (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012
Kaiser Purchased Tax Credits Indemnity Reserve [Member]
Loss Contingencies [Line Items]
Loss Contingency Accrual, at Carrying Value Beginning Balance	$ 21.5
Loss Contingency, Accrual Carrying Value, Foreign Exchange Impact	0.4
Loss Contingency Accrual, at Carrying Value Ending Balance	21.9
Kaiser Tax, Civil and Labor Indemnity Reserve [Member]
Loss Contingencies [Line Items]
Loss Contingency Accrual, at Carrying Value Beginning Balance	9.1
Loss Contingency, Accrual Carrying Value, Foreign Exchange Impact	0.2
Loss Contingency Accrual, at Carrying Value Ending Balance	9.3
Kaiser Total indemnity reserves
Loss Contingencies [Line Items]
Loss Contingency Accrual, at Carrying Value Beginning Balance	30.6
Loss Contingency, Accrual Carrying Value, Foreign Exchange Impact	0.6
Loss Contingency Accrual, at Carrying Value Ending Balance	$ 31.2