Fair Value (Narrative) (Details) (USD $)	Dec. 31, 2013	Sep. 30, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, carrying value	$ 1,602,961,000	$ 1,263,232,000
Senior Notes [Member] | 6.5% Senior Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Stated interest rate	6.50%	6.50%
Long-term debt, carrying value	657,961,000	658,232,000
Principal amount	650,000,000
Long-term debt, fair value	$ 698,800,000
Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Credit valuation adjustment to total fair value percentage (less than 1%)	1.00%