Goodwill and Other Intangible Assets (Narrative) (Details)	3 Months Ended	9 Months Ended	12 Months Ended
	Apr. 30, 2017 USD ($) reporting_unit	Apr. 30, 2017 USD ($)	Jul. 31, 2017 USD ($)	Jul. 31, 2016 USD ($)	Jul. 31, 2015 USD ($)
Indefinite-lived Intangible Assets [Line Items]
Goodwill impairment	$ 0	$ 0	$ 0	$ 0
Number of reporting units | reporting_unit	5
Percentage of a reporting units fair value in excess of carrying amount	60.00%	60.00%
Goodwill			238,100,000	229,300,000	$ 223,700,000
Fair value inputs, long-term revenue growth rate		3.00%
Fair value inputs, discount rate		11.50%
Goodwill, impairment test, benchmark residual growth rate decrease that would result in potential impairment, percent	3.00%	3.00%
Goodwill, impairment test, benchmark discount rate increase that would result in potential impairment, percent	0.00%	0.00%
Goodwill, impairment test, benchmark projected cash flow decrease that would result in potential impairment, percent	1.50%	1.50%
Intangible assets, net			40,600,000	38,500,000
Gas Turbine Systems
Indefinite-lived Intangible Assets [Line Items]
Percentage of a reporting units fair value in excess of carrying amount	15.00%	15.00%
Goodwill	$ 60,400,000	$ 60,400,000
Customer Relationships
Indefinite-lived Intangible Assets [Line Items]
Intangible assets, net			$ 30,800,000	30,700,000
Acquired finite-lived intangible assets, weighted average useful life			11 years 10 months 24 days
Patents, Trademarks and Technology
Indefinite-lived Intangible Assets [Line Items]
Intangible assets, net			$ 9,800,000	$ 7,800,000
Acquired finite-lived intangible assets, weighted average useful life			8 years 1 month 6 days