Fair Value Measurements (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Fair value \| Senior unsecured notes
Long-term Debt
Fixed rate senior unsecured notes	$ 315.0	$ 309.8
Carrying value \| Senior unsecured notes
Long-term Debt
Fixed rate senior unsecured notes	298.3	298.3
Carrying value \| Other long-term debt
Long-term Debt
Fixed rate senior unsecured notes	$ 506.1	$ 438.8

- Definition

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents notes payable as of the balance sheet date.

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