Long-Term Debt (Summary Of Long-Term Debt) (Details) (USD $)	Jun. 30, 2012	Sep. 30, 2011	Jun. 30, 2012 Senior Notes [Member] 6.5% Senior Notes [Member]	Jan. 31, 2012 Senior Notes [Member] 6.5% Senior Notes [Member]	Sep. 30, 2011 Senior Notes [Member] 6.5% Senior Notes [Member]	Jun. 30, 2012 Line of Credit [Member] 2011 Credit Facility [Member]	Sep. 30, 2011 Line of Credit [Member] 2011 Credit Facility [Member]	Jun. 30, 2011 Line of Credit [Member] 2011 Credit Facility [Member]
Line of Credit Facility [Line Items]
Principal amount			$ 450,000,000	$ 450,000,000	$ 0
Outstanding credit facility	150,000,000					205,000,000	520,000,000
Long-term debt	$ 655,000,000	$ 520,000,000
Interest rate			6.50%	6.50%
Market adjustable interest rate (per annum)						3.30%	3.10%	3.10%