Revenue - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jul. 31, 2019	Jul. 31, 2018	Jul. 31, 2019	Jul. 31, 2018
Disaggregation of Revenue [Line Items]
Total revenue	$ 960,606	$ 818,817	$ 2,604,144	$ 2,194,930
Products and services at a point in time
Disaggregation of Revenue [Line Items]
Total revenue	815,470		2,178,571
Services transferred over time
Disaggregation of Revenue [Line Items]
Total revenue	145,136		425,573
Converged Packet Optical
Disaggregation of Revenue [Line Items]
Total revenue	724,245		1,897,080
Packet Networking
Disaggregation of Revenue [Line Items]
Total revenue	71,823		216,529
Platform Software and Services
Disaggregation of Revenue [Line Items]
Total revenue	37,312		114,139
Blue Planet Automation Software and Services
Disaggregation of Revenue [Line Items]
Total revenue	10,530		37,977
Maintenance Support and Training
Disaggregation of Revenue [Line Items]
Total revenue	65,936		196,002
Installation and Deployment
Disaggregation of Revenue [Line Items]
Total revenue	39,802		111,746
Consulting and Network Design
Disaggregation of Revenue [Line Items]
Total revenue	10,958		30,671
Networking Platforms | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue	796,068	677,451	2,113,609	1,765,166
Networking Platforms | Operating Segments | Products and services at a point in time
Disaggregation of Revenue [Line Items]
Total revenue	796,068		2,113,609
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	724,245	592,892	1,897,080	1,548,189
Networking Platforms | Operating Segments | Packet Networking
Disaggregation of Revenue [Line Items]
Total revenue	71,823	84,559	216,529	216,977
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	47,842	41,183	152,116	133,415
Software and Software-Related Services | Operating Segments | Products and services at a point in time
Disaggregation of Revenue [Line Items]
Total revenue	14,598		51,017
Software and Software-Related Services | Operating Segments | Services transferred over time
Disaggregation of Revenue [Line Items]
Total revenue	33,244		101,099
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	37,312	36,818	114,139	117,347
Software and Software-Related Services | Operating Segments | Blue Planet Automation Software and Services
Disaggregation of Revenue [Line Items]
Total revenue	10,530	4,365	37,977	16,068
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	116,696	100,183	338,419	296,349
Global Services | Operating Segments | Products and services at a point in time
Disaggregation of Revenue [Line Items]
Total revenue	4,804		13,945
Global Services | Operating Segments | Services transferred over time
Disaggregation of Revenue [Line Items]
Total revenue	111,892		324,474
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	65,936	60,897	196,002	177,759
Global Services | Operating Segments | Installation and Deployment
Disaggregation of Revenue [Line Items]
Total revenue	39,802	31,262	111,746	89,487
Global Services | Operating Segments | Consulting and Network Design
Disaggregation of Revenue [Line Items]
Total revenue	$ 10,958	$ 8,024	$ 30,671	$ 29,103