Debt and Credit Facilities (Borrowing Obligations) (Detail) (USD $)	Dec. 31, 2013	Sep. 30, 2013
Debt Instrument [Line Items]
Credit Facility, net of unamortized discount of $1.1 million and $1.2 million, respectively.	$ 479,875,000	$ 481,016,000
Total long-term debt	2,361,277,000	2,354,131,000
Less: current portion	248,518,000	246,040,000
Non-current portion of long-term debt	2,112,759,000	2,108,091,000
5.375% Senior Notes due August 15, 2020
Debt Instrument [Line Items]
Debt instrument, stated interest rate	5.375%	5.375%
Debt Instrument, Interest Rate, Effective Percentage	5.283%	5.28%
Debt Instrument Maturity Year	2020
Unamortized Premium	(5,200,000)	(5,400,000)
Senior Notes, net of unamortized premium	1,055,190,000	1,055,385,000
Convertible Debentures Two Point Seven Five Percent Due November One Twenty Thirty One [Member]
Debt Instrument [Line Items]
Debt instrument, stated interest rate	2.75%	2.75%
Debt Instrument, Interest Rate, Effective Percentage	7.43%	7.43%
Debt Instrument Maturity Year	2031
Debt instrument, unamortized discount	107,500,000	113,500,000
Convertible Debentures, net of unamortized discount	582,529,000	576,524,000
2.75% Convertible Debentures due August 15, 2027
Debt Instrument [Line Items]
Debt instrument, stated interest rate	2.75%	2.75%
Debt Instrument, Interest Rate, Effective Percentage	7.30%	7.30%
Debt Instrument Maturity Year	2027
Debt instrument, unamortized discount	6,300,000	8,800,000
Convertible Debentures, net of unamortized discount	243,683,000	241,206,000
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Debt instrument, unamortized discount	$ (1,100,000)	$ (1,200,000)