Income Tax Uncertainties (Details) (USD $) In Millions	9 Months Ended
Sep. 30, 2011	Dec. 31, 2010
Income Tax Uncertainties
Unrecognized tax benefits, including penalties and interest, that if recognized would impact the effective tax rate	$ 8.4	$ 6.6
Unrecognized tax benefits, including penalties and interest, net of federal benefit that, if recognized, would affect the effective tax rate	6.0	4.6
Accrued interest and penalties related to uncertain tax positions	2.2	1.9
Accrued interest and penalties related to uncertain tax positions, net of federal benefit	1.8	1.5
Total expense for of interest and penalties, net of federal benefit related to uncertain tax positions	0.3
Estimated decrease in unrecognized tax benefits within the next 12-month period, lower end of range	0.2
Estimated decrease in unrecognized tax benefits within the next 12-month period, upper end of range	1.9
Estimated decrease in unrecognized tax benefits net of federal benefits within the next 12-month period, lower end of range	0.2
Estimated decrease in unrecognized tax benefits net of federal benefits within the next 12-month period, upper end of range	$ 1.3

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The estimated lower bound of the reasonably possible change in the total amount of the unrecognized tax benefit (that will significantly increase or decrease within twelve months of the balance sheet date) for a tax position taken.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 740

-SubTopic 10

-Section 50

-Paragraph 15

-Subparagraph (d)

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The estimated upper bound of the reasonably possible change in the total amount of the unrecognized tax benefit (that will significantly increase or decrease within twelve months of the balance sheet date) for a tax position taken.

+ References

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- Definition

This element represents the total of accruals as of the date of the statement of financial position for interest recognized for an underpayment of income taxes computed by applying the applicable statutory rate of interest to the difference between a tax position recognized for financial reporting purposes and the amount previously taken or expected to be taken in a tax return of the entity and the amount of statutory penalties for a tax position claimed or expected to be claimed by the entity, in its tax return, that does not meet the minimum statutory threshold to avoid payment of penalties.

+ References

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

-Publisher FASB

-Name FASB Interpretation (FIN)

-Number 48

-Paragraph 21

-Subparagraph c

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name FASB Interpretation (FIN)

-Number 48

-Paragraph 15, 16

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 740

-SubTopic 10

-Section 50

-Paragraph 15

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32718-109319

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The estimated lower bound of the reasonably possible change in the total amount of the unrecognized tax benefit net of federal tax benefits (that will significantly increase or decrease within twelve months of the balance sheet date) for a tax position taken.

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The estimated upper bound of the reasonably possible change in the total amount of the unrecognized tax benefit net of federal tax benefits (that will significantly increase or decrease within twelve months of the balance sheet date) for a tax position taken.

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This element represents the total of accruals net of federal tax benefits as of the date of the statement of financial position for interest recognized for an underpayment of income taxes computed by applying the applicable statutory rate of interest to the difference between a tax position recognized for financial reporting purposes and the amount previously taken or expected to be taken in a tax return of the entity and the amount of statutory penalties for a tax position claimed or expected to be claimed by the entity, in its tax return, that does not meet the minimum statutory threshold to avoid payment of penalties.

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This element represents the total of interest expense, net of federal benefit, recognized for an underpayment of income taxes computed by applying the applicable statutory rate of interest to the difference between a tax position recognized for financial reporting purposes and the amount previously taken or expected to be taken in a tax return of the entity and the amount of statutory penalties in the period in which the entity claims or expects to claim a tax position, in its tax return, that does not meet the minimum statutory threshold to avoid payment of penalties.

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The total amount of unrecognized tax benefits that, if recognized, would impact the effective tax rate, including accrued penalties and interest.

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The total amount of unrecognized tax benefits net of federal tax benefits that, if recognized, would affect the effective tax rate, including accrued penalties and interest.

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