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License Agreement, Fee Receivable Period

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License Agreement, Number of Installments Payable

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License Agreement, Payment Period

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License Agreement, Sale of Intangible Asset

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Patents and Licenses, Fully-paid, Non-Exclusive Field of Use Term

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For unclassified balance sheet, amounts due from customers or clients for goods or services that have been delivered or sold in the normal course of business.

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Revenue earned during the period relating to consideration received from another party for the right to use, but not own, certain of the entity's intangible assets. Licensing arrangements include, but are not limited to, rights to use a patent, copyright, technology, manufacturing process, software or trademark. Licensing fees are generally, but not always, fixed as to amount and not dependent upon the revenue generated by the licensing party. An entity may receive licensing fees for licenses that also generate royalty payments to the entity.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Amount due from parties in nontrade transactions, classified as other.

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Cash received from licensees for license fees during the current period.

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The cash inflow from disposal of asset without physical form usually arising from contractual or other legal rights, excluding goodwill.

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License, Settlement and Release Agreements (Details) $ in Thousands																								12 Months Ended
	Feb. 28, 2018 USD ($)	Dec. 29, 2017 USD ($)	Jun. 30, 2017 USD ($)	Apr. 21, 2017 USD ($)	Mar. 31, 2017 USD ($)	Mar. 24, 2017 USD ($)	Mar. 02, 2017 USD ($)	Jan. 13, 2017 USD ($)	Dec. 28, 2016 USD ($)	Sep. 01, 2016 USD ($)	Jun. 30, 2016 USD ($)	Jun. 27, 2016 USD ($)	Jun. 06, 2016 USD ($)	Jun. 03, 2016 USD ($)	Mar. 31, 2016 USD ($)	Jan. 14, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 30, 2015 USD ($)	Sep. 30, 2015 USD ($)	Apr. 22, 2015 USD ($)	Apr. 07, 2015 USD ($)	Jan. 16, 2015 USD ($)	Sep. 24, 2014 USD ($) installment_payment	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Mar. 31, 2019 USD ($)	Jan. 31, 2019 USD ($)	Mar. 31, 2018 USD ($)	Jan. 31, 2018 USD ($)
License and Settlement Agreement \| Licensing Agreements \| Subsequent Event
Loss Contingencies [Line Items]
Sale of patent in license agreement	$ 65,000
Payment period	20 days
Fee receivable period	4 years
Additional license fees	$ 45,000
FireEye License \| Licensing Agreements
Loss Contingencies [Line Items]
Sale of patent in license agreement		$ 17,500
Receivable related to license agreement		5,000																						$ 12,500
License fee receivable		5,000
EU Licensee \| Licensing Agreements
Loss Contingencies [Line Items]
Sale of patent in license agreement				$ 4,900
Payment period				10 days
Receivable related to license agreement				$ 2,300
Cash received from license agreement			$ 2,300
License revenue																								1,300
EU Licensee \| Licensing Agreements \| Forecast
Loss Contingencies [Line Items]
Receivable related to license agreement																											$ 1,300		$ 1,300
Sophos Inc \| Licensing Agreements
Loss Contingencies [Line Items]
Receivable related to license agreement																								$ 2,500
Cash received from license agreement					$ 15,000
License revenue					$ 15,000
Sophos Inc \| Licensing Agreements \| Forecast
Loss Contingencies [Line Items]
Receivable related to license agreement																										$ 1,250		$ 1,250
Avast Software s.r.o. \| Licensing Agreements
Loss Contingencies [Line Items]
Cash received from license agreement						$ 7,745
Veracode, Inc, \| Licensing Agreements
Loss Contingencies [Line Items]
Cash received from license agreement							$ 2,000
F5 Networks, Inc. \| Licensing Agreements
Loss Contingencies [Line Items]
Sale of patent in license agreement																									$ 4,000
License revenue																									4,000
European Cloud-Based Network Security Firm
Loss Contingencies [Line Items]
Sale of patent in license agreement											$ 565
Proofpoint and Amorize Technologies
Loss Contingencies [Line Items]
Sale of patent in license agreement														$ 10,900
Receivable related to license agreement		$ 3,300																							3,300
License fee receivable																									10,900
Cash received from license agreement									$ 3,300				$ 4,300
License revenue																									7,600
United States-based third party \| Licensing Agreements
Loss Contingencies [Line Items]
Sale of patent in license agreement																		$ 3,650
License fee receivable																	$ 3,650
Cash received from license agreement										$ 1,000		$ 1,650						$ 1,000
License revenue																	$ 1,000								$ 2,650
F-Secure Corporation
Loss Contingencies [Line Items]
Fully-paid, non-exclusive field of use license term (in years)																					2 years
F-Secure Corporation \| Patents
Loss Contingencies [Line Items]
Sale of patent in license agreement																					$ 1,000
License fee receivable																			$ 1,000
Cash received from license agreement															$ 300					$ 700
License revenue															$ 300				$ 700
Websense \| Licensing Agreements
Loss Contingencies [Line Items]
License fee receivable																							$ 8,000
Number of installment payments \| installment_payment																							4
License agreement installment								$ 1,000								$ 2,000						$ 2,000	$ 3,000