The charge against earnings in the period for known or estimated future costs arising from requirements to perform environmental remediation activities.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Statement of Position (SOP)

-Number 96-1

-Paragraph 147, 148, 149, 150

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 143

-Paragraph 2

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Emerging Issues Task Force (EITF)

-Number 90-8

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Statement of Position (SOP)

-Number 96-1

-Paragraph 170

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 5

-Paragraph 9, 10

Name:	us-gaap_EnvironmentalRemediationExpense
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Environmental (Details) (USD $) In Millions	3 Months Ended		9 Months Ended
Environmental (Details) (USD $) In Millions	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010	Dec. 31, 2010
Loss Contingencies [Line Items]
Environmental remediation costs	$ 0.7	$ 1.5	$ 0.6	$ 1.5
Accrued environmental liability	30.3		30.3		26.2
Frontier [Member]
Loss Contingencies [Line Items]
Accrued environmental liability	7.3		7.3
Frontier [Member] \| Other Long-Term Liabilities [Member]
Loss Contingencies [Line Items]
Accrued environmental liability	4.9		4.9
Other Long-Term Liabilities [Member]
Loss Contingencies [Line Items]
Accrued environmental liability	$ 22.1		$ 22.1		$ 20.4