Long-Term Debt (Summary of Long-Term Debt) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013		Jun. 21, 2013	Sep. 30, 2012
Debt Instrument [Line Items]
Long-term debt	$ 1,338,500			$ 830,000
Senior Notes [Member] | 6.5% Senior Notes [Member]
Debt Instrument [Line Items]
Long-term debt	658,500			450,000
Stated interest rate	6.50%		6.50%	6.50%
Market adjustable interest rate (per annum)			6.26%
Revolving Credit Facility [Member] | 2011 Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Long-term debt	$ 680,000			$ 380,000
Market adjustable interest rate (per annum)	3.00%	[1]		3.20%	[1]

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