Intangible Assets (Details) - USD ($)	3 Months Ended		6 Months Ended		12 Months Ended
	Jan. 31, 2019	Jan. 31, 2018	Jan. 31, 2019	Jan. 31, 2018	Jul. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	$ 361,095,000		$ 361,095,000		$ 361,095,000
Accumulated amortization	128,876,000		128,876,000		120,299,000
Net carrying amount	232,219,000		232,219,000		$ 240,796,000
Amortization of intangibles	4,288,000	$ 5,268,000	8,577,000	$ 10,537,000
Amortization expense - year one	17,155,000		17,155,000
Amortization expense - year two	17,155,000		17,155,000
Amortization expense - year three	16,196,000		16,196,000
Amortization expense - year four	14,955,000		14,955,000
Amortization expense - year five	14,955,000		$ 14,955,000
Customer Relationships
Finite-Lived Intangible Assets [Line Items]
Weighted average amortization period			21 years		21 years
Gross carrying amount	249,831,000		$ 249,831,000		$ 249,831,000
Accumulated amortization	60,587,000		60,587,000		55,350,000
Net carrying amount	189,244,000		$ 189,244,000		$ 194,481,000
Technologies
Finite-Lived Intangible Assets [Line Items]
Weighted average amortization period			12 years 9 months 15 days		12 years 9 months 15 days
Gross carrying amount	82,370,000		$ 82,370,000		$ 82,370,000
Accumulated amortization	56,783,000		56,783,000		54,386,000
Net carrying amount	25,587,000		$ 25,587,000		$ 27,984,000
Trademarks and other
Finite-Lived Intangible Assets [Line Items]
Weighted average amortization period			16 years 4 months 22 days		16 years 4 months 22 days
Gross carrying amount	28,894,000		$ 28,894,000		$ 28,894,000
Accumulated amortization	11,506,000		11,506,000		10,563,000
Net carrying amount	$ 17,388,000		$ 17,388,000		$ 18,331,000