Acquisitions (Details) - USD ($)			1 Months Ended	3 Months Ended
	Jul. 01, 2017	Mar. 04, 2015	Sep. 30, 2015	Jul. 31, 2016	Jul. 30, 2017	Jan. 29, 2017
Business Acquisition [Line Items]
Effective date of acquisition	Jul. 01, 2017	Mar. 04, 2015
Name of acquired entity	AptoVision Technologies Inc.	Triune Systems, L.L.C.
Goodwill					$ 346,575,000	$ 329,703,000
AptoVision Technologies Inc. [Member]
Business Acquisition [Line Items]
Cash paid to to acquire business	$ 17,600,000
Earn-out liability	17,000,000
Costs incurred during the acquisition	900,000
Goodwill	$ 16,872,000				16,872,000
AptoVision Technologies Inc. [Member] | Earn-out Payable Within First Three Fiscal Years Of Acquisition Date [Member]
Business Acquisition [Line Items]
Period over which contingent consideration will be paid	3 years
Triune Systems [Member]
Business Acquisition [Line Items]
Cash paid to to acquire business		$ 35,000,000	$ 9,500,000	$ 500,000
Potential payments under earn-out arrangements, high estimate		70,000,000
Earn-out liability					$ 0
Guaranteed minimum purchase price		45,000,000
Additional cash consideration		$ 10,000,000
Triune Systems [Member] | Earn-out Payable Within First Three Fiscal Years Of Acquisition Date [Member]
Business Acquisition [Line Items]
Period over which contingent consideration will be paid		3 years
Triune Systems [Member] | Additional Earn-out Payable After Third Fiscal Year From Acquisition Date [Member]
Business Acquisition [Line Items]
Potential payments under earn-out arrangements, high estimate		$ 16,000,000
Maximum [Member] | AptoVision Technologies Inc. [Member]
Business Acquisition [Line Items]
Potential payments under earn-out arrangements, high estimate	$ 47,000,000
Accrued Liabilities [Member] | AptoVision Technologies Inc. [Member]
Business Acquisition [Line Items]
Earn-out liability	8,500,000
Other long-term liabilities [Member] | AptoVision Technologies Inc. [Member]
Business Acquisition [Line Items]
Earn-out liability	$ 8,500,000