Income Taxes (Details Textuals) (USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Taxes (Textuals) [Abstract]
Alternative minimum tax credits			$ 271.2
Foreign tax credits			74.7
General business credits			71.1
Capital loss			66.2
State net operating loss carryforwards			40.3
Foreign loss carryforwards included in Company's tax credits and loss carryforwards			1,034.5
Valuation allowance reserve for U.S. capital losses, state NOLs, foreign NOLs and certain foreign deferred tax assets	(714.9)		(656.4)	(714.9)
Minerals resource rent tax, net of federal tax	77.2		87.4	(77.2)	0
MRRT market value allowance deferred tax asset			1,230.4
Minerals resource rent tax deferred liability			(237.2)
Valuation allowance minerals resource rent tax	766.9		977.7	766.9
Change in unrecognized tax benefit			21.1
Net Unrecognized Tax Benefit	119.7		140.5	119.7
Accrued interest related to unrecognized tax benefits included in income tax provision			(36.0)	21.2	11.4
Accrued interest related to uncertain tax positions	47.4		11.4	47.4
Tax adjustments, settlements, and unusual provisions		20.3
ATO proposed assessment penalties and interest			28.1
ATO proposed assessment tax			20.3
ATO Proposed Assessment Interest			7.8
ATO Settlement Deposit			$ 32.7