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Fair Value Measurement (Details) (USD $)
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Sep. 30, 2013
NESA
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Nov. 02, 2012
NESA
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Sep. 30, 2013
Jacobs Trading, LLC
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Sep. 30, 2012
Jacobs Trading, LLC
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Oct. 02, 2011
Jacobs Trading, LLC
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Sep. 30, 2013
Recurring basis
Level 1
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Sep. 30, 2012
Recurring basis
Level 1
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Sep. 30, 2013
Recurring basis
Level 2
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Sep. 30, 2012
Recurring basis
Level 2
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Sep. 30, 2013
Recurring basis
Level 3
NESA
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Sep. 30, 2012
Recurring basis
Level 3
Jacobs Trading, LLC
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|---|---|---|---|---|---|---|---|---|---|---|---|
| Fair value measurement | |||||||||||
| Assets, fair value | $ 0 | $ 0 | $ 0 | $ 0 | |||||||
| Liabilities, fair value | 0 | 0 | 0 | 0 | |||||||
| Estimated fair value of earn-out | $ 18,300,000 | $ 18,000,000 | $ 0 | $ 14,500,000 | $ 8,300,000 | $ 18,390,000 | $ 14,511,000 |