Discontinued Operations (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	May 31, 2014	Jan. 31, 2014	Dec. 31, 2013
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income (loss) from discontinued operations before income taxes	$ 7.6	$ (62.1)	$ 8.6	$ (94.8)
Income tax provision (benefit)	2.6	(19.0)	2.6	(28.3)
Income (loss) from discontinued operations, net of income taxes	5.0	(43.1)	6.0	(66.5)
Total revenues associated with discontinued operations		38.6		106.3
Other current assets	1.6		1.6				38.6
Investments and other assets	20.2		20.2				47.4
Total assets classified as discontinued operations	21.8		21.8				86.0
Accounts payable and accrued expenses	19.6		19.6				127.8
Other noncurrent liabilities	84.7		84.7				90.2
Total liabilities classified as discontinued operations	104.3		104.3				218.0
Payment to Patriot based on the construct of the negotiated settlement						70
Asset retirement obligation	724.1		724.1				712.8
Potential cash proceeds from sale of property held-for-sale					70
Wilkie Creek [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Liability balance	12.8		12.8				36.6
Change in estimate			(3.6)
Cash payments			(20.6)
Foreign currency remeasurement expense			0.4
Asset retirement obligation	48.0		48.0
Net gain on agreement termination, before tax	4.6		4.6
Net gain on agreement termination, after tax	3.2		3.2
Impairment charge, before tax		45.2		45.2
Impairment charge, after tax		32.4		32.4
Wilkie Creek [Member] | Other Exit Costs [Domain]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Liability balance	0.1		0.1				2.7
Change in estimate			(0.2)
Cash payments			(2.4)
Foreign currency remeasurement expense			0
Wilkie Creek [Member] | Accrued Take or Pay Liabilities [Domain]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Liability balance	12.7		12.7				33.9
Change in estimate			(3.4)
Cash payments			(18.2)
Foreign currency remeasurement expense			$ 0.4