Debt (Narrative) (Details) (USD $)	3 Months Ended	12 Months Ended
	Dec. 31, 2012	Sep. 30, 2010	Sep. 30, 2012
Principal amount	$ 287,500,000		$ 287,500,000
Interest rate	2.50%
Maturity date	Apr. 15, 2015
Number of equity instruments on convertible debt	5,500,000
Convertible conversion rate	19.10
Principal amount on conversion rate	1,000
Convertible conversion price	$ 52.35
Percentage of purchase price of notes which should be paid upon a fundamental change	100.00%
Remaining discount amortization period	2 years 3 months 15 days
Equity component of senior convertible notes issuance	56,300,000		56,300,000
Proceeds from Notes		279,000,000
Net cost of Note Hedges and Warrants		34,100,000
Payment for Note Hedges		60,100,000
Proceeds from sale of Warrants		26,100,000
Note Hedges, shares of common stock covered	5,500,000
Hedge transations, strike price per share	$ 52.35
Number of common stock shares acquired through sale of warrants	5,500,000
Warrants sold, common stock strike price	73.29
Conversion Trigger, One [Member]
Number of days out of 30 that common stock price exceeded conversion price	20
Number of consecutive trading days in period	30 days
Percent of conversion price	130.00%
Conversion Trigger, Two [Member]
Principal amount on conversion rate	$ 1,000
Number of consecutive trading days in period	5 days
Subsequent period	5 days
Percentage of product, maximum	98.00%