Fair Value (Schedule Of Financial Instruments Measured At Fair Value On Recurring Basis) (Details) - USD ($) $ in Millions	Mar. 31, 2017	Sep. 30, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration	$ 10.7
Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	494.6	$ 408.7
Auction rate security	0.0	2.3
Total	494.6	411.0
Contingent consideration	15.7	7.9
Total	15.7	7.9
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	494.6	408.7
Auction rate security	0.0	0.0
Total	494.6	408.7
Contingent consideration	0.0	0.0
Total	0.0	0.0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	0.0	0.0
Auction rate security	0.0	0.0
Total	0.0	0.0
Contingent consideration	0.0	0.0
Total	0.0	0.0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	0.0	0.0
Auction rate security	0.0	2.3
Total	0.0	2.3
Contingent consideration	15.7	7.9
Total	$ 15.7	$ 7.9