Intangible Assets (Details) - USD ($)			3 Months Ended
	Oct. 31, 2017	Jul. 31, 2017	Oct. 31, 2017	Oct. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	$ 361,095,000	$ 361,095,000	$ 361,095,000
Accumulated amortization	104,493,000	99,224,000	104,493,000
Net carrying amount	256,602,000	$ 261,871,000	256,602,000
Amortization of intangibles			5,269,000	$ 6,055,000
Amortization expense - year one	21,075,000		21,075,000
Amortization expense - year two	17,155,000		17,155,000
Amortization expense - year three	17,155,000		17,155,000
Amortization expense - year four	16,196,000		16,196,000
Amortization expense - year five	$ 14,955,000		14,955,000
Customer Relationships
Finite-Lived Intangible Assets [Line Items]
Weighted average amortization period	20 years 3 months 18 days	20 years 3 months 18 days
Gross carrying amount	$ 249,831,000	$ 249,831,000	249,831,000
Accumulated amortization	45,280,000	41,923,000	45,280,000
Net carrying amount	$ 204,551,000	$ 207,908,000	204,551,000
Technologies
Finite-Lived Intangible Assets [Line Items]
Weighted average amortization period	12 years 3 months 18 days	12 years 3 months 18 days
Gross carrying amount	$ 82,370,000	$ 82,370,000	82,370,000
Accumulated amortization	50,064,000	48,623,000	50,064,000
Net carrying amount	$ 32,306,000	$ 33,747,000	32,306,000
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	9,149,000	8,678,000	9,149,000
Net carrying amount	$ 19,745,000	$ 20,216,000	$ 19,745,000