Segment and Geographic Information (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 30, 2019 USD ($) Segment	Mar. 31, 2018 USD ($)	Mar. 30, 2019 USD ($) Segment	Mar. 31, 2018 USD ($)
Number of operating segments | Segment			2
Number of reportable segments | Segment	2
Revenue	$ 290,451	$ 307,883	$ 625,140	$ 614,527
Operating Costs	79,904	83,708	157,256	166,743
Gross margin	210,547	224,175	467,884	447,784
Sales and marketing	103,722	98,390	207,940	197,765
General and administrative	35,371	33,369	73,235	68,389
Restructuring and other charges, net	26,980	114	45,473	219
Amortization of acquired intangible assets	5,930	7,895	11,866	15,716
Operating income	(22,858)	22,210	7,186	39,526
Interest expense	(11,383)	(10,379)	(21,659)	(20,426)
Other income (expense), net	(821)	285	(1,475)	1,083
Income (loss) before income taxes	(33,420)	11,546	(12,998)	18,017
Operating Segments
Revenue	290,451	307,883	625,140	614,527
Operating Costs	126,239	133,295	249,730	267,844
Gross margin	164,212	174,588	375,410	346,683
Operating Segments | Americas [Member]
Revenue	119,717	128,479	261,570	255,485
Operating Segments | Europe [Member]
Revenue	119,045	121,641	230,397	243,107
Operating Segments | Asia Pacific [Member]
Revenue	51,689	57,763	133,173	115,935
Unallocated
Sales and marketing	94,200	93,352	188,696	187,848
General and administrative	25,856	27,398	51,627	54,846
Amortization of acquired intangible assets	12,772	14,451	25,425	28,947
Stock-based compensation	26,967	17,026	56,374	35,357
Other unallocated operating expenses	295	37	629	(60)
Restructuring Plan 2019 [Member]
Restructuring and other charges, net			16,000
Prior Headquarters [Member] | Unallocated
Restructuring and other charges, net	26,980	114	45,473	219
Solutions | Operating Segments
Revenue	251,171	274,994	550,413	552,663
IoT | Operating Segments
Revenue	39,280	32,889	74,727	61,864
Calculated under Revenue Guidance in Effect before Topic 606 [Member]
Revenue	315,499	307,883	654,256	614,527
Operating Costs	77,967		153,163
Gross margin	237,532		501,093
Sales and marketing	109,421		216,725
General and administrative	35,371		73,235
Restructuring and other charges, net	26,980		45,473
Amortization of acquired intangible assets	5,930		11,866
Operating income	(1,572)		31,610
Interest expense	(11,383)		(21,659)
Other income (expense), net	(1,065)		(1,613)
Income (loss) before income taxes	(11,890)		11,564
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Operating Segments
Revenue	315,499		654,256
Operating Costs	124,302		245,637
Gross margin	191,197		408,619
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Operating Segments | Americas [Member]
Revenue	137,774		272,671
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Operating Segments | Europe [Member]
Revenue	123,247		243,404
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Operating Segments | Asia Pacific [Member]
Revenue	54,478		138,181
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Unallocated
Sales and marketing	99,899		197,481
General and administrative	25,856		51,627
Amortization of acquired intangible assets	12,772		25,425
Stock-based compensation	26,967		56,374
Other unallocated operating expenses	295		629
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Prior Headquarters [Member] | Unallocated
Restructuring and other charges, net	26,980		45,473
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Solutions | Operating Segments
Revenue	272,936		571,098
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | IoT | Operating Segments
Revenue	42,563		83,158
Software Products | Operating Segments
Revenue	249,521	262,453	542,764	527,643
Operating Costs	93,913	97,349	185,541	197,081
Gross margin	155,608	165,104	357,223	330,562
Software Products | Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Operating Segments
Revenue	276,901		576,289
Operating Costs	93,386		184,231
Gross margin	183,515		392,058
Professional Services | Operating Segments
Revenue	40,930	45,430	82,376	86,884
Operating Costs	32,326	35,946	64,189	70,763
Gross margin	8,604	$ 9,484	18,187	$ 16,121
Professional Services | Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Operating Segments
Revenue	38,598		77,967
Operating Costs	30,916		61,406
Gross margin	$ 7,682		$ 16,561