Marketable Securities (Details) (USD $) In Millions	Sep. 30, 2011	Sep. 30, 2010
Marketable Securities
Amortized Cost	$ 297.5	$ 297.4
Gross Unrealized Gains	0.2	0.3
Gross Unrealized Losses	(0.1)
Fair Value	297.6	297.7
Obligations of U.S. government agencies [Member]
Marketable Securities
Amortized Cost	73.7	131.0
Gross Unrealized Gains	0.1	0.2
Fair Value	73.8	131.2
U.S. Treasury securities [Member]
Marketable Securities
Amortized Cost	16.3	1.0
Fair Value	16.3	1.0
Corporate debt securities issued under the FDIC Temporary Liquidity Guarantee Program [Member]
Marketable Securities
Amortized Cost	103.7	100.9
Gross Unrealized Gains	0.1	0.1
Fair Value	103.8	101.0
Corporate debt securities [Member]
Marketable Securities
Amortized Cost	98.8	39.9
Gross Unrealized Losses	(0.1)
Fair Value	98.7	39.9
Foreign government securities [Member]
Marketable Securities
Amortized Cost		14.6
Fair Value		14.6
Total debt securities [Member]
Marketable Securities
Amortized Cost	292.5	287.4
Gross Unrealized Gains	0.2	0.3
Gross Unrealized Losses	(0.1)
Fair Value	292.6	287.7
Certificates of deposit [Member]
Marketable Securities
Amortized Cost	5.0	10.0
Fair Value	$ 5.0	$ 10.0

For an unclassified balance sheet, total of debt securities categorized neither as held-to-maturity nor trading.

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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.

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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.

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+ Details