Fair Value Measurements - Level 3 Liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Jul. 31, 2017	Jul. 31, 2016	Jul. 31, 2015
Reconciliation of liability measured and recorded at fair value on a recurring basis using Level 3
Beginning balance	$ 1,579	$ 2,777	$ 5,869
Total net unrealized (gains) losses included in general and administrative expense in earnings	(265)	(687)	(2,585)
Net purchases, issuances, sales and settlements	(176)	(511)	(507)
Ending balance	1,138	1,579	2,777
Jet Prep Contingent Consideration | Jet Prep Ltd.
Reconciliation of liability measured and recorded at fair value on a recurring basis using Level 3
Beginning balance	0	751	2,722
Total net unrealized (gains) losses included in general and administrative expense in earnings	0	(751)	(1,971)
Net purchases, issuances, sales and settlements	0	0	0
Ending balance	0	0	751
Jet Prep Assumed Contingent Obligation | Jet Prep Ltd.
Reconciliation of liability measured and recorded at fair value on a recurring basis using Level 3
Beginning balance	1,138	1,138	1,752
Total net unrealized (gains) losses included in general and administrative expense in earnings	0	0	(614)
Net purchases, issuances, sales and settlements	0	0	0
Ending balance	1,138	1,138	1,138
Cantel Medical (U.K.) Contingent Guaranteed Obligation | Cantel Medical (UK) - PuriCore International Limited
Reconciliation of liability measured and recorded at fair value on a recurring basis using Level 3
Beginning balance	441	888	1,395
Total net unrealized (gains) losses included in general and administrative expense in earnings	(265)	64	0
Net purchases, issuances, sales and settlements	(176)	(511)	(507)
Ending balance	$ 0	$ 441	$ 888