Fair Value Measurements (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013
Liabilities
Long-term debt, amortized cost	$ 1,811,641	$ 1,690,703
Fair value measurement on recurring basis | Total
Assets
Cash equivalents	27,000
Total assets	27,511	152
Liabilities
Long-term debt	1,874,444	1,753,822
Total liabilities	1,874,491	1,753,858
Fair value measurement on recurring basis | Foreign exchange contracts | Total
Assets
Foreign exchange derivative	511	152
Liabilities
Foreign exchange derivative	47	36
Fair value measurement on recurring basis | Level 1
Assets
Cash equivalents	27,000
Total assets	27,000
Liabilities
Long-term debt	1,870,250	1,671,500
Total liabilities	1,870,250	1,671,500
Fair value measurement on recurring basis | Level 2
Assets
Total assets	511	152
Liabilities
Long-term debt	4,194	82,322
Total liabilities	4,241	82,358
Fair value measurement on recurring basis | Level 2 | Foreign exchange contracts
Assets
Foreign exchange derivative	511	152
Liabilities
Foreign exchange derivative	$ 47	$ 36