Commitments and Contingencies Obligation Reserves (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 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 Changes in Estimate	0
Loss Contingency, Accrual Carrying Value, Foreign Exchange Impact	(1.5)
Loss Contingency Accrual, at Carrying Value Ending Balance	20.0
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 Changes in Estimate	0
Loss Contingency, Accrual Carrying Value, Foreign Exchange Impact	(0.7)
Loss Contingency Accrual, at Carrying Value Ending Balance	8.4
Kaiser Total indemnity reserves
Loss Contingencies [Line Items]
Loss Contingency Accrual, at Carrying Value Beginning Balance	30.6
Loss Contingency, Accrual Carrying Value Changes in Estimate	0
Loss Contingency, Accrual Carrying Value, Foreign Exchange Impact	(2.2)
Loss Contingency Accrual, at Carrying Value Ending Balance	$ 28.4