Revenue - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Apr. 30, 2019	Apr. 30, 2018	Apr. 30, 2019	Apr. 30, 2018
Disaggregation of Revenue [Line Items]
Total revenue	$ 865,011	$ 729,978	$ 1,643,538	$ 1,376,113
Products and services at a point in time
Disaggregation of Revenue [Line Items]
Total revenue	716,699		1,363,103
Services transferred over time
Disaggregation of Revenue [Line Items]
Total revenue	148,312		280,435
Converged Packet Optical
Disaggregation of Revenue [Line Items]
Total revenue	623,838		1,172,835
Packet Networking
Disaggregation of Revenue [Line Items]
Total revenue	73,138		144,707
Platform Software and Services
Disaggregation of Revenue [Line Items]
Total revenue	35,229		76,827
Blue Planet Automation Software and Services
Disaggregation of Revenue [Line Items]
Total revenue	12,473		27,447
Maintenance Support and Training
Disaggregation of Revenue [Line Items]
Total revenue	68,788		130,065
Installation and Deployment
Disaggregation of Revenue [Line Items]
Total revenue	41,322		71,944
Consulting and Network Design
Disaggregation of Revenue [Line Items]
Total revenue	10,223		19,713
Networking Platforms | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue	696,976	591,682	1,317,542	1,087,715
Networking Platforms | Operating Segments | Products and services at a point in time
Disaggregation of Revenue [Line Items]
Total revenue	696,976		1,317,542
Networking Platforms | Operating Segments | Services transferred over time
Disaggregation of Revenue [Line Items]
Total revenue	0		0
Networking Platforms | Operating Segments | Converged Packet Optical
Disaggregation of Revenue [Line Items]
Total revenue	623,838	527,867	1,172,835	955,297
Networking Platforms | Operating Segments | Packet Networking
Disaggregation of Revenue [Line Items]
Total revenue	73,138	63,815	144,707	132,418
Networking Platforms | Operating Segments | Platform Software and Services
Disaggregation of Revenue [Line Items]
Total revenue	0		0
Networking Platforms | Operating Segments | Blue Planet Automation Software and Services
Disaggregation of Revenue [Line Items]
Total revenue	0		0
Networking Platforms | Operating Segments | Maintenance Support and Training
Disaggregation of Revenue [Line Items]
Total revenue	0		0
Networking Platforms | Operating Segments | Installation and Deployment
Disaggregation of Revenue [Line Items]
Total revenue	0		0
Networking Platforms | Operating Segments | Consulting and Network Design
Disaggregation of Revenue [Line Items]
Total revenue	0		0
Software and Software-Related Services | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue	47,702	38,745	104,274	92,232
Software and Software-Related Services | Operating Segments | Products and services at a point in time
Disaggregation of Revenue [Line Items]
Total revenue	14,148		36,420
Software and Software-Related Services | Operating Segments | Services transferred over time
Disaggregation of Revenue [Line Items]
Total revenue	33,554		67,854
Software and Software-Related Services | Operating Segments | Converged Packet Optical
Disaggregation of Revenue [Line Items]
Total revenue	0		0
Software and Software-Related Services | Operating Segments | Packet Networking
Disaggregation of Revenue [Line Items]
Total revenue	0		0
Software and Software-Related Services | Operating Segments | Platform Software and Services
Disaggregation of Revenue [Line Items]
Total revenue	35,229	36,393	76,827	80,529
Software and Software-Related Services | Operating Segments | Blue Planet Automation Software and Services
Disaggregation of Revenue [Line Items]
Total revenue	12,473	2,352	27,447	11,703
Software and Software-Related Services | Operating Segments | Maintenance Support and Training
Disaggregation of Revenue [Line Items]
Total revenue	0		0
Software and Software-Related Services | Operating Segments | Installation and Deployment
Disaggregation of Revenue [Line Items]
Total revenue	0		0
Software and Software-Related Services | Operating Segments | Consulting and Network Design
Disaggregation of Revenue [Line Items]
Total revenue	0		0
Global Services | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue	120,333	99,551	221,722	196,166
Global Services | Operating Segments | Products and services at a point in time
Disaggregation of Revenue [Line Items]
Total revenue	5,575		9,141
Global Services | Operating Segments | Services transferred over time
Disaggregation of Revenue [Line Items]
Total revenue	114,758		212,581
Global Services | Operating Segments | Converged Packet Optical
Disaggregation of Revenue [Line Items]
Total revenue	0		0
Global Services | Operating Segments | Packet Networking
Disaggregation of Revenue [Line Items]
Total revenue	0		0
Global Services | Operating Segments | Platform Software and Services
Disaggregation of Revenue [Line Items]
Total revenue	0		0
Global Services | Operating Segments | Blue Planet Automation Software and Services
Disaggregation of Revenue [Line Items]
Total revenue	0		0
Global Services | Operating Segments | Maintenance Support and Training
Disaggregation of Revenue [Line Items]
Total revenue	68,788	60,904	130,065	116,862
Global Services | Operating Segments | Installation and Deployment
Disaggregation of Revenue [Line Items]
Total revenue	41,322	28,209	71,944	58,225
Global Services | Operating Segments | Consulting and Network Design
Disaggregation of Revenue [Line Items]
Total revenue	$ 10,223	$ 10,438	$ 19,713	$ 21,079