Fair Value of Financial Instruments (Details) (USD $)	Dec. 31, 2012	Sep. 30, 2012
Debt instruments
Estimated fair value of long-term debt	$ 8,100,000	$ 12,500,000
Carrying value of long-term debt	7,400,000	11,500,000
Assets and liabilities measured at fair value on a recurring basis | Level 1
Assets
Cash equivalents	128,080,000	171,300,000
Total assets measured at fair value	128,080,000	171,300,000
Assets and liabilities measured at fair value on a recurring basis | Level 2
Assets
Current derivative assets	2,552,000	3,779,000
Non-current derivative assets	2,612,000	3,713,000
Total assets measured at fair value	5,164,000	7,492,000
Liabilities
Current derivative liabilities	5,564,000	6,839,000
Non-current derivative liabilities	4,304,000	6,498,000
Total liabilities measured at fair value	9,868,000	13,337,000
Assets and liabilities measured at fair value on a recurring basis | Level 3
Liabilities
Fair value of additional contingent cash consideration	11,684,000
Total liabilities measured at fair value	11,684,000
Assets and liabilities measured at fair value on a recurring basis | Total
Assets
Cash equivalents	128,080,000	171,300,000
Current derivative assets	2,552,000	3,779,000
Non-current derivative assets	2,612,000	3,713,000
Total assets measured at fair value	133,244,000	178,792,000
Liabilities
Current derivative liabilities	5,564,000	6,839,000
Non-current derivative liabilities	4,304,000	6,498,000
Fair value of additional contingent cash consideration	11,684,000
Total liabilities measured at fair value	$ 21,552,000	$ 13,337,000