Fair Value Measurements (Narrative) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2011	Sep. 30, 2010 Airgas [Member]
Available-for-sale securities		$ 102.5
Unrealized appreciation of this investment carried at fair value, after tax		20.6
Unrealized appreciation of this investment carried at fair value		$ 32.9
Agreements to purchase the remaining shares	25.00%

For an unclassified balance sheet, this item represents investments in debt and equity securities which are categorized neither as held-to-maturity nor trading.

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+ Details