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Segments and Entity-Wide Disclosures - Revenue, Profit (Loss) and Net Income (Loss) Reconciliation (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Apr. 30, 2019	Apr. 30, 2018	Apr. 30, 2019	Apr. 30, 2018
Revenue:
Total revenue	$ 865,011	$ 729,978	$ 1,643,538	$ 1,376,113
Segment profit:
Operating income (loss)	80,320	32,066	128,263	48,802
Less: Non-performance operating expenses
Selling and marketing	103,502	97,359	201,615	185,874
General and administrative	42,154	38,976	81,397	77,382
Amortization of intangible assets	5,529	3,623	11,057	7,246
Significant asset impairments and restructuring costs	4,068	4,359	6,341	10,320
Acquisition and integration costs	1,135	0	2,743	0
Add: Other non-performance financial items
Interest expense and other income (loss), net	(9,715)	(11,735)	(14,903)	(23,894)
Less: Provision for income taxes	17,867	6,475	27,006	484,415
Net income (loss)	52,738	13,856	86,354	(459,507)
Operating Segments
Segment profit:
Operating income (loss)	236,708	176,383	431,416	329,624
Operating Segments \| Networking Platforms
Revenue:
Total revenue	696,976	591,682	1,317,542	1,087,715
Segment profit:
Operating income (loss)	175,191	126,823	311,782	215,392
Operating Segments \| Software and Software-Related Services
Revenue:
Total revenue	47,702	38,745	104,274	92,232
Segment profit:
Operating income (loss)	6,536	8,276	24,952	82,321
Operating Segments \| Global Services
Revenue:
Total revenue	120,333	99,551	221,722	196,166
Segment profit:
Operating income (loss)	54,981	41,284	94,682	31,911
Converged Packet Optical
Revenue:
Total revenue	623,838		1,172,835
Converged Packet Optical \| Operating Segments \| Networking Platforms
Revenue:
Total revenue	623,838	527,867	1,172,835	955,297
Converged Packet Optical \| Operating Segments \| Software and Software-Related Services
Revenue:
Total revenue	0		0
Converged Packet Optical \| Operating Segments \| Global Services
Revenue:
Total revenue	0		0
Packet Networking
Revenue:
Total revenue	73,138		144,707
Packet Networking \| Operating Segments \| Networking Platforms
Revenue:
Total revenue	73,138	63,815	144,707	132,418
Packet Networking \| Operating Segments \| Software and Software-Related Services
Revenue:
Total revenue	0		0
Packet Networking \| Operating Segments \| Global Services
Revenue:
Total revenue	0		0
Platform Software and Services
Revenue:
Total revenue	35,229		76,827
Platform Software and Services \| Operating Segments \| Networking Platforms
Revenue:
Total revenue	0		0
Platform Software and Services \| Operating Segments \| Software and Software-Related Services
Revenue:
Total revenue	35,229	36,393	76,827	80,529
Platform Software and Services \| Operating Segments \| Global Services
Revenue:
Total revenue	0		0
Blue Planet Automation Software and Services
Revenue:
Total revenue	12,473		27,447
Blue Planet Automation Software and Services \| Operating Segments \| Networking Platforms
Revenue:
Total revenue	0		0
Blue Planet Automation Software and Services \| Operating Segments \| Software and Software-Related Services
Revenue:
Total revenue	12,473	2,352	27,447	11,703
Blue Planet Automation Software and Services \| Operating Segments \| Global Services
Revenue:
Total revenue	0		0
Maintenance Support and Training
Revenue:
Total revenue	68,788		130,065
Maintenance Support and Training \| Operating Segments \| Networking Platforms
Revenue:
Total revenue	0		0
Maintenance Support and Training \| Operating Segments \| Software and Software-Related Services
Revenue:
Total revenue	0		0
Maintenance Support and Training \| Operating Segments \| Global Services
Revenue:
Total revenue	68,788	60,904	130,065	116,862
Installation and Deployment
Revenue:
Total revenue	41,322		71,944
Installation and Deployment \| Operating Segments \| Networking Platforms
Revenue:
Total revenue	0		0
Installation and Deployment \| Operating Segments \| Software and Software-Related Services
Revenue:
Total revenue	0		0
Installation and Deployment \| Operating Segments \| Global Services
Revenue:
Total revenue	41,322	28,209	71,944	58,225
Consulting and Network Design
Revenue:
Total revenue	10,223		19,713
Consulting and Network Design \| Operating Segments \| Networking Platforms
Revenue:
Total revenue	0		0
Consulting and Network Design \| Operating Segments \| Software and Software-Related Services
Revenue:
Total revenue	0		0
Consulting and Network Design \| Operating Segments \| Global Services
Revenue:
Total revenue	$ 10,223	$ 10,438	$ 19,713	$ 21,079