FAIR VALUE MEASUREMENTS - Schedule of Assets and Liabilities as Presented on Ciena's Condensed Consolidated Balance Sheets (Details) - USD ($) $ in Thousands	Aug. 01, 2026	Nov. 01, 2025
Assets:
Total assets measured at fair value	$ 2,529,387	$ 1,198,881
Liabilities:
Total liabilities measured at fair value	11,003	7,659
Level 1
Assets:
Total assets measured at fair value	2,118,814	927,807
Liabilities:
Total liabilities measured at fair value	0	0
Level 2
Assets:
Total assets measured at fair value	410,573	271,074
Liabilities:
Total liabilities measured at fair value	11,003	7,659
Level 3
Assets:
Total assets measured at fair value	0	0
Liabilities:
Total liabilities measured at fair value	0	0
Balance Sheet Location [Axis]: us-gaap:AccruedLiabilitiesCurrent
Liabilities:
Accrued liabilities and other short-term obligations	11,003	6,314
Balance Sheet Location [Axis]: us-gaap:AccruedLiabilitiesCurrent \| Level 1
Liabilities:
Accrued liabilities and other short-term obligations	0	0
Balance Sheet Location [Axis]: us-gaap:AccruedLiabilitiesCurrent \| Level 2
Liabilities:
Accrued liabilities and other short-term obligations	11,003	6,314
Balance Sheet Location [Axis]: us-gaap:AccruedLiabilitiesCurrent \| Level 3
Liabilities:
Accrued liabilities and other short-term obligations	0	0
Balance Sheet Location [Axis]: us-gaap:CashAndCashEquivalentsAtCarryingValue
Assets:
Cash equivalents	2,099,862	901,176
Balance Sheet Location [Axis]: us-gaap:CashAndCashEquivalentsAtCarryingValue \| Level 1
Assets:
Cash equivalents	2,087,490	901,077
Balance Sheet Location [Axis]: us-gaap:CashAndCashEquivalentsAtCarryingValue \| Level 2
Assets:
Cash equivalents	12,372	99
Balance Sheet Location [Axis]: us-gaap:CashAndCashEquivalentsAtCarryingValue \| Level 3
Assets:
Cash equivalents	0	0
Balance Sheet Location [Axis]: us-gaap:MarketableSecuritiesNoncurrent
Assets:
Long-term investments	213,553	57,142
Balance Sheet Location [Axis]: us-gaap:MarketableSecuritiesNoncurrent \| Level 1
Assets:
Long-term investments	0	0
Balance Sheet Location [Axis]: us-gaap:MarketableSecuritiesNoncurrent \| Level 2
Assets:
Long-term investments	213,553	57,142
Balance Sheet Location [Axis]: us-gaap:MarketableSecuritiesNoncurrent \| Level 3
Assets:
Long-term investments	0	0
Balance Sheet Location [Axis]: us-gaap:OtherAssetsNoncurrent
Assets:
Other assets	27,357	21,179
Balance Sheet Location [Axis]: us-gaap:OtherAssetsNoncurrent \| Level 1
Assets:
Other assets	27,357	21,179
Balance Sheet Location [Axis]: us-gaap:OtherAssetsNoncurrent \| Level 2
Assets:
Other assets	0	0
Balance Sheet Location [Axis]: us-gaap:OtherAssetsNoncurrent \| Level 3
Assets:
Other assets	0	0
Balance Sheet Location [Axis]: us-gaap:OtherLiabilitiesNoncurrent
Liabilities:
Other long-term obligations		1,345
Balance Sheet Location [Axis]: us-gaap:OtherLiabilitiesNoncurrent \| Level 1
Liabilities:
Other long-term obligations		0
Balance Sheet Location [Axis]: us-gaap:OtherLiabilitiesNoncurrent \| Level 2
Liabilities:
Other long-term obligations		1,345
Balance Sheet Location [Axis]: us-gaap:OtherLiabilitiesNoncurrent \| Level 3
Liabilities:
Other long-term obligations		0
Balance Sheet Location [Axis]: us-gaap:PrepaidExpenseAndOtherAssetsCurrent
Assets:
Other assets	4,322	3,236
Balance Sheet Location [Axis]: us-gaap:PrepaidExpenseAndOtherAssetsCurrent \| Level 1
Assets:
Other assets	0	0
Balance Sheet Location [Axis]: us-gaap:PrepaidExpenseAndOtherAssetsCurrent \| Level 2
Assets:
Other assets	4,322	3,236
Balance Sheet Location [Axis]: us-gaap:PrepaidExpenseAndOtherAssetsCurrent \| Level 3
Assets:
Other assets	0	0
Balance Sheet Location [Axis]: us-gaap:ShortTermInvestments
Assets:
Short-term investments	184,293	216,148
Balance Sheet Location [Axis]: us-gaap:ShortTermInvestments \| Level 1
Assets:
Short-term investments	3,967	5,551
Balance Sheet Location [Axis]: us-gaap:ShortTermInvestments \| Level 2
Assets:
Short-term investments	180,326	210,597
Balance Sheet Location [Axis]: us-gaap:ShortTermInvestments \| Level 3
Assets:
Short-term investments	$ 0	$ 0