Fair Value (Details) (USD $)	Mar. 31, 2013	Dec. 31, 2012
Fair Value Disclosures [Abstract]
Senior notes, fair value	$ 506,100,000
Senior notes, carrying value	$ 498,165,000	$ 498,124,000

- 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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