Fair Value Measurements - Level 3 Liabilities (Details) - USD ($)	3 Months Ended	9 Months Ended
Apr. 30, 2017	Jan. 31, 2017	Oct. 31, 2016	Jul. 31, 2016	Apr. 30, 2016	Jan. 31, 2016	Oct. 31, 2015	Apr. 30, 2017
Reconciliation of liability measured and recorded at fair value on a recurring basis using Level 3
Beginning balance	$ 1,461,000	$ 1,487,000	$ 1,579,000	$ 1,855,000	$ 1,918,000	$ 2,050,000	$ 2,777,000	$ 1,579,000
Total net unrealized (gains) losses included in general and administrative expense in earnings	(283,000)	9,000	9,000	(136,000)	20,000	21,000	(592,000)
Settlements	(48,000)	(47,000)	(70,000)	(196,000)	(95,000)	(100,000)	(120,000)
Foreign currency translation	8,000	12,000	(31,000)	56,000	12,000	(53,000)	(15,000)
Ending balance	1,138,000	1,461,000	1,487,000	1,579,000	1,855,000	1,918,000	2,050,000	1,138,000
Impairment of long-lived assets, including goodwill and intangibles with indefinite lives								0
Contingent Consideration \| Jet Prep Ltd.
Reconciliation of liability measured and recorded at fair value on a recurring basis using Level 3
Beginning balance				148,000	143,000	139,000	751,000
Total net unrealized (gains) losses included in general and administrative expense in earnings				(148,000)	5,000	4,000	(612,000)
Ending balance					148,000	143,000	139,000
Assumed contingent liability \| Jet Prep Ltd.
Reconciliation of liability measured and recorded at fair value on a recurring basis using Level 3
Beginning balance	1,138,000	1,138,000	1,138,000	1,138,000	1,138,000	1,138,000	1,138,000	1,138,000
Ending balance	1,138,000	1,138,000	1,138,000	1,138,000	1,138,000	1,138,000	1,138,000	1,138,000
Contingent guaranteed obligation \| Cantel Medical (UK)
Reconciliation of liability measured and recorded at fair value on a recurring basis using Level 3
Beginning balance	323,000	349,000	441,000	569,000	637,000	773,000	888,000	$ 441,000
Total net unrealized (gains) losses included in general and administrative expense in earnings	(283,000)	9,000	9,000	12,000	15,000	17,000	20,000
Settlements	(48,000)	(47,000)	(70,000)	(196,000)	(95,000)	(100,000)	(120,000)
Foreign currency translation	$ 8,000	12,000	(31,000)	56,000	12,000	(53,000)	(15,000)
Ending balance		$ 323,000	$ 349,000	$ 441,000	$ 569,000	$ 637,000	$ 773,000

Amount of write-down of assets recognized in the income statement. Includes, but is not limited to, losses from tangible assets, intangible assets and goodwill.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 45
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=68055307&loc=d3e2420-110228

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Amount of gain (loss) recognized on the income statement for financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Amount of gain (loss) recognized in other comprehensive income (loss) for financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Amount of settlements of financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Fair value of financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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