Discontinued Operations (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Jan. 31, 2014	Dec. 31, 2013
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss from discontinued operations before income taxes	$ (0.1)	$ (16.6)
Income tax benefit	0.3	7.5
Income (loss) from discontinued operations, net of income taxes	0.2	(9.1)
Total revenues associated with discontinued operations		32.1
Other current assets	3.1			38.6
Investments and other assets	21.9			47.4
Total assets classified as discontinued operations	25.0			86.0
Accounts payable and accrued expenses	47.2			127.8
Other noncurrent liabilities	87.9			90.2
Total liabilities classified as discontinued operations	135.1			218.0
Payment to Patriot based on the construct of the negotiated settlement			70.0
Asset Retirement Obligation	715.2			712.8
Wilkie Creek [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Asset Retirement Obligation	48.2
Beginning and ending liability balance | Wilkie Creek [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total liabilities classified as discontinued operations	31.6			36.6
Accrued Take-or-Pay liabilities	31.3			33.9
Other Exit Costs	0.3			2.7
Cash Payments | Wilkie Creek [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total liabilities classified as discontinued operations	(5.9)
Accrued Take-or-Pay liabilities	(3.5)
Other Exit Costs	(2.4)
Foreign currency remeasurement expense | Wilkie Creek [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total liabilities classified as discontinued operations	0.9
Accrued Take-or-Pay liabilities	0.9
Other Exit Costs	$ 0