Debt - Summary of Long-Term Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Sep. 30, 2015
Debt Instrument [Line Items]
Long-term Debt	$ 1,608,399	$ 1,678,268
Senior Notes | 6.5% Senior Notes
Debt Instrument [Line Items]
Stated interest rate	6.50%	6.50%
Long-term Debt	$ 648,399	$ 648,268
Revolving Credit Facility
Debt Instrument [Line Items]
Long-term Debt	$ 960,000	$ 1,030,000