Net Earnings (Loss) Per Common Unitholders' Interest (Schedule of Earnings Per Share) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended	12 Months Ended
Jul. 31, 2014	Apr. 30, 2014	Jan. 31, 2014	Oct. 31, 2013	Jul. 31, 2013	Apr. 30, 2013	Jan. 31, 2013	Oct. 31, 2012	Jul. 31, 2014	Jul. 31, 2013	Jul. 31, 2012
Earnings Per Share [Abstract]
Common unitholders' interest in net earnings (loss)	$ (47,317)	$ 44,931	$ 59,860	$ (24,595)	$ (28,516)	$ 44,234	$ 55,069	$ (17,481)	$ 32,879	$ 55,862	$ (10,842)
Weighted average common units outstanding									79,651,100	79,038,600	77,572,400
Dilutive securities									20,600	37,000	0
Weighted Average Number of Shares Outstanding, Basic and Diluted									79,671,700	79,075,600	77,572,400
Basic and diluted net earnings (loss) per common unitholders' interest	$ (0.58)	$ 0.57	$ 0.72	$ (0.31)	$ (0.36)	$ 0.56	$ 0.70	$ (0.22)	$ 0.41	$ 0.71	$ (0.14)

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Aggregate amount of net income allocated to limited partners.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section S99

-Paragraph 5

-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187171-122770

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- Definition

The amount of net income or loss for the period per each limited partnership and general partnership unit in instances when basic and diluted earnings per unit are the same amount and aggregated on the face of the financial statements. Basic earnings per unit is the amount of net income or loss for the period per unit outstanding during the reporting period. Diluted earnings per unit includes the amount of net income or loss for the period available to each limited and general partnership unit outstanding during the reporting period and to each unit that would have been outstanding assuming the issuance of units for all dilutive potential units outstanding during the reporting period.

+ References

No definition available.

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- Definition

The average number of shares or units issued and outstanding that are used in calculating diluted EPS or earnings per unit (EPU), determined based on the timing of issuance of shares or units in the period.

+ References

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- Definition

Average number of shares or units issued and outstanding that are used in calculating basic and diluted earnings per share (EPS).

+ References

No definition available.

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- Definition

Number of [basic] shares or units, after adjustment for contingently issuable shares or units and other shares or units not deemed outstanding, determined by relating the portion of time within a reporting period that common shares or units have been outstanding to the total time in that period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 260

-SubTopic 10

-Section 50

-Paragraph 1

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 260

-SubTopic 10

-Section 45

-Paragraph 10

-URI http://asc.fasb.org/extlink&oid=7655603&loc=d3e1448-109256

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Weighted-Average Number of Common Shares Outstanding

-URI http://asc.fasb.org/extlink&oid=6528421

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