Acquisitions - BHT (Details) - USD ($) $ in Thousands								12 Months Ended
		Aug. 23, 2017	Apr. 01, 2017	Sep. 26, 2016	Aug. 01, 2016	Mar. 01, 2016	Sep. 14, 2015	Jul. 31, 2017		Jul. 31, 2016	Jul. 31, 2015
Business Acquisition [Line Items]
Goodwill								$ 311,445		$ 280,318	$ 241,951
BHT | Subsequent Events
Business Acquisition [Line Items]
Total consideration, excluding acquisition costs		$ 61,236
CR Kennedy
Business Acquisition [Line Items]
Cash paid								11,999
Debt acquired								0
Total			$ 11,999					11,999
Property and equipment								0
Goodwill								5,894
Deferred income taxes								0
Other working capital								1,905
Total								11,999
CR Kennedy | Customer relationships
Business Acquisition [Line Items]
Amortizable intangible assets:								4,200
CR Kennedy | Technology
Business Acquisition [Line Items]
Amortizable intangible assets:								0
CR Kennedy | Brand names
Business Acquisition [Line Items]
Amortizable intangible assets:								0
Vantage(1)
Business Acquisition [Line Items]
Cash paid	[1]							4,044
Debt acquired	[1]							0
Total				$ 4,044				4,044	[1]
Property and equipment	[1]							433
Goodwill	[1]							2,299
Deferred income taxes	[1]							0
Other working capital	[1]							320
Total	[1]							4,044
Vantage(1) | Customer relationships
Business Acquisition [Line Items]
Amortizable intangible assets:	[1]							992
Vantage(1) | Technology
Business Acquisition [Line Items]
Amortizable intangible assets:	[1]							0
Vantage(1) | Brand names
Business Acquisition [Line Items]
Amortizable intangible assets:	[1]							0
Accutron
Business Acquisition [Line Items]
Cash paid	[1]							53,049
Debt acquired	[1]							0
Total	[1]				$ 53,049			53,049
Property and equipment	[1]							1,676
Goodwill	[1]							21,989
Deferred income taxes	[1]							112
Other working capital	[1]							4,472
Total	[1]							53,049
Accutron | Customer relationships
Business Acquisition [Line Items]
Amortizable intangible assets:	[1]							12,800
Accutron | Technology
Business Acquisition [Line Items]
Amortizable intangible assets:	[1]							10,000
Accutron | Brand names
Business Acquisition [Line Items]
Amortizable intangible assets:	[1]							$ 2,000
NAMSA
Business Acquisition [Line Items]
Cash paid										13,424
Debt acquired	[1]									0
Total	[1]					$ 13,424				13,424
Property and equipment	[1]									437
Goodwill	[1]									3,687
Deferred income taxes	[1]									0
Other working capital	[1]									2,160
Total	[1]									13,424
NAMSA | Customer relationships
Business Acquisition [Line Items]
Amortizable intangible assets:	[1]									5,820
NAMSA | Technology
Business Acquisition [Line Items]
Amortizable intangible assets:	[1]									1,320
NAMSA | Brand names
Business Acquisition [Line Items]
Amortizable intangible assets:	[1]									0
MI
Business Acquisition [Line Items]
Cash paid										79,597
Debt acquired										0
Total							$ 79,597			79,597
Property and equipment										6,464
Goodwill										40,006
Deferred income taxes										(8,683)
Other working capital										4,420
Total										79,597
MI | Customer relationships
Business Acquisition [Line Items]
Amortizable intangible assets:										24,430
MI | Technology
Business Acquisition [Line Items]
Amortizable intangible assets:										10,930
MI | Brand names
Business Acquisition [Line Items]
Amortizable intangible assets:										$ 2,030

[1] The excess purchase price over net assets acquired was assigned to goodwill, all of which is deductible for income tax purposes.