Long-Term Debt (Summary of Long-Term Debt) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013		Sep. 30, 2013
Debt Instrument [Line Items]
Long-term debt	$ 1,602,961		$ 1,263,232
Senior Notes [Member] | 6.5% Senior Notes [Member]
Debt Instrument [Line Items]
Long-term debt	657,961		658,232
Stated interest rate	6.50%		6.50%
Revolving Credit Facility [Member] | 2011 Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Long-term debt	$ 945,000		$ 605,000
Market adjustable interest rate (per annum)	2.80%	[1]	3.00%	[1]

[1] After the impact of our interest rate swaps.