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Fair Value Measurements, Available-For-Sale Securities And Restricted Funds (Narrative) (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2012	Dec. 31, 2011
Fair Value Measurements, Available-For-Sale Securities And Restricted Funds [Abstract]
Estimated available-for-sale securities in unrealized losses positions	$ 14.7	$ 67.0
Number of mutual funds investments in a gross unrealized losses position	204	294

- Definition

This item represents the aggregate fair value of investments in debt and equity securities in an unrealized loss position which are categorized neither as held-to-maturity nor trading securities.

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