Debt (Narrative) (Details) (USD $) Share data in Millions, except Per Share data, unless otherwise specified	12 Months Ended
	Sep. 30, 2012 Y	Sep. 30, 2011	Sep. 30, 2010
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 287,500,000	$ 287,500,000
Debt Instrument, Interest Rate, Stated Percentage	2.50%
Debt Instrument, Maturity Date	Apr. 15, 2015
Debt Instrument, Convertible, Number of Equity Instruments	5,500,000
Debt Instrument, Convertible, Conversion Ratio	19.10
Debt Instrument, Convertible, Conversion Price	$ 52.35
Percentage of purchase price of notes which should be paid upon a fundamental change	100.00%
Debt Instrument, Convertible, Remaining Discount Amortization Period	2.5
Equity component of the senior convertible notes issuance	56,300,000	56,300,000
Proceeds from Notes Payable			279,000,000
Debt Instrument, Net Cost			34,100,000
Payment For Note Hedge			60,100,000
Proceeds from Issuance of Warrants	0	0	49,716,000
Note Hedged Shares Of Common Stock Covered	5.5
Strike Price For Note Hedges	$ 52.35
Convertible Notes [Member]
Debt Instrument [Line Items]
Proceeds from Issuance of Warrants			26,100,000
Conversion Trigger, One [Member]
Debt Instrument [Line Items]
Number Of Days Out Of 30 That Common Stock Price Exceeded Conversion Price	20
Percent Of Conversion Price	130.00%
Debt instrument, Convertible, Conversion Trigger, Trading Window	30 days
Conversion Trigger, Two [Member]
Debt Instrument [Line Items]
Debt Instrument, Convertible, Principal Amount on Conversion Rate	$ 1,000
Debt instrument, Convertible, Conversion Trigger, Percentage of Product, Maximum	98.00%
Debt instrument, Convertible, Conversion Trigger, Trading Window	5 days
Debt instrument, Convertible, Conversion Trigger, Subsequent Period	5 days
Common Stock
Debt Instrument [Line Items]
Number Of Common Stock Shares Acquired Through Sale Of Warrants	5.5
Warrants Sold Common Stock Strike Price	73.29