Fair Value Measurements - Additional Information (Detail) - USD ($) $ in Thousands	Apr. 30, 2018	Jul. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Goodwill, Carrying Value	$ 435,426	$ 437,697
Debt, Fair Value	61,794	109,303
Debt, Carrying Value	58,157	104,536
Workplace Safety [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Goodwill, Carrying Value	$ 45,954	$ 45,833