Long-Term Debt (Narrative) (Details) (Line of Credit [Member], 2011 Credit Facility [Member], USD $)	3 Months Ended
	Dec. 31, 2012	Sep. 30, 2012
Line of Credit [Member] | 2011 Credit Facility [Member]
Line of Credit Facility [Line Items]
Outstanding credit facility	$ 620,000,000	$ 380,000,000
Revolving credit facility, term	5 years
Maximum borrowing capacity	$ 750,000,000
Revolving credit facility, initiation date	May 31, 2011
Credit facility variable rate	Eurodollar
Credit facility basis spread on variable rate	2.50%