Long-Term Debt (Summary Of Long-Term Debt) (Details) (USD $)	Mar. 31, 2012	Sep. 30, 2011	Mar. 31, 2012 2011 Credit Facility [Member]	Sep. 30, 2011 2011 Credit Facility [Member]	Jun. 30, 2011 2011 Credit Facility [Member]	Mar. 31, 2012 6.50 % Senior Notes [Member]	Jan. 31, 2012 6.50 % Senior Notes [Member]
Line of Credit Facility [Line Items]
Principal amount						$ 450,000,000	$ 450,000,000
Outstanding credit facility	50,000,000		150,000,000	520,000,000
Long-term debt	$ 600,000,000	$ 520,000,000
Market adjustable interest rate (per annum)			3.30%	3.10%	3.10%
Interest rate						6.50%	6.50%