v3.10.0.1

Summary of Significant Accounting Policies - Additional Information (Detail)		12 Months Ended
	Jan. 16, 2015 USD ($)	Jul. 31, 2018 USD ($) Facility Segment	Jul. 31, 2017 USD ($)	Jul. 31, 2016 USD ($)	Oct. 31, 2017 USD ($)	Jul. 31, 2014 USD ($)
Schedule Of Significant Accounting Policies [Line Items]
Number of reportable segments \| Segment		2
Allowances for accounts receivables		$ 219,000	$ 263,000
Depreciation expense		14,800,000	12,700,000	$ 12,900,000
Depreciation related to restructuring and realignment				300,000
Goodwill		233,204,000	224,391,000	22,228,000
Asset retirement obligations recognized						$ 3,700,000
Non-cash Impairment charges		0	0	0
Foreign currency translation resulting in gains (loss)		(700,000)	2,500,000	(2,600,000)
Performance Materials
Schedule Of Significant Accounting Policies [Line Items]
Goodwill		225,329,000	216,528,000	14,504,000	$ 225,300,000
Goodwill allocated on sale of business	$ 700,000
Electronic Chemicals
Schedule Of Significant Accounting Policies [Line Items]
Goodwill		$ 7,875,000	$ 7,863,000	$ 7,724,000	$ 7,900,000
United States
Schedule Of Significant Accounting Policies [Line Items]
Number of pipeline performance business facilities \| Facility		4
Canada
Schedule Of Significant Accounting Policies [Line Items]
Number of pipeline performance business facilities \| Facility		1

Number of pipeline performance business facilities.

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The carrying amount of a liability for an asset retirement obligation associated with the disposal or retirement of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset including clean-up obligations of lessee.

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Schedule Of Significant Accounting Policies.

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A valuation allowance for trade and other receivables due to an Entity within one year (or the normal operating cycle, whichever is longer) that are expected to be uncollectible.

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The amount of expense recognized in the current period that reflects the allocation of the cost of tangible assets over the assets' useful lives. Includes production and non-production related depreciation.

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Amount before tax of foreign currency transaction realized and unrealized gain (loss) recognized in the income statement.

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Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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Amount of divestiture of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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The aggregate amount of write-downs for impairments recognized during the period for long-lived assets held for abandonment, exchange or sale.

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Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

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Amount of expense or loss included in net income that result in no cash flow, classified as other.

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KMG CHEMICALS INC 10-K