Revenue from Contracts with Customers (Disaggregation of Revenue) (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 29, 2018	Dec. 30, 2017
Disaggregation of Revenue [Line Items]
Revenue	$ 334,689	$ 306,644
Subscription license
Disaggregation of Revenue [Line Items]
Revenue	63,517
Subscription support & cloud services
Disaggregation of Revenue [Line Items]
Revenue	77,424
Subscription Services
Disaggregation of Revenue [Line Items]
Revenue	140,941
Perpetual support
Disaggregation of Revenue [Line Items]
Revenue	110,497
Recurring Services
Disaggregation of Revenue [Line Items]
Revenue	251,438
Perpetual license
Disaggregation of Revenue [Line Items]
Revenue	41,805
Software
Disaggregation of Revenue [Line Items]
Revenue	293,243	265,190
Professional services
Disaggregation of Revenue [Line Items]
Revenue	41,446	41,454
Calculated under Revenue Guidance in Effect before Topic 606 [Member]
Disaggregation of Revenue [Line Items]
Revenue	338,757	306,644
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Subscription Services
Disaggregation of Revenue [Line Items]
Revenue	148,413	100,008
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Perpetual support
Disaggregation of Revenue [Line Items]
Revenue	109,225	131,197
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Recurring Services
Disaggregation of Revenue [Line Items]
Revenue	257,638	231,205
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Perpetual license
Disaggregation of Revenue [Line Items]
Revenue	41,750	33,985
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Software
Disaggregation of Revenue [Line Items]
Revenue	299,388	265,190
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Professional services
Disaggregation of Revenue [Line Items]
Revenue	$ 39,369	$ 41,454