Assets and Liabilities, at Fair Value Level 4 - Available for Sale Securities in OCI (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012
Assets and Liabilities, at Fair Value [Abstract]
Equity Investments in Exchange Stock - Cost	$ 4.4
Equity Investments in Exchange Stock - Fair Value	12.0
Equity Investments in Exchange Stock - LME Shares Fair Value	8.4
Accumulated Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax - LME Shares	(6.1)
Deferred Tax Liabilities, Accumulated Other Comprehensive Income - LME Shares	1.9
Accumulated Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax - Other Exchange Shares	0.3
Deferred Tax Assets, Accumulated Other Comprehensive Income - Other Exchange Shares	$ (0.2)