Refers to number of putative class action complaints against entity.

No definition available.

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Namespace Prefix:	lll_
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- Definition

Refers to number of putative class action complaints against entity and officers.

+ References

No definition available.

+ Details

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Namespace Prefix:	lll_
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- Definition

The amount recovered from insurance. These recoveries reduce costs and losses that are reported as a separate line item under operating expenses.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.3)
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

+ Details

Name:	us-gaap_InsuranceRecoveries
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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount awarded to other party in judgment or settlement of litigation.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

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.

+ References

No definition available.

+ Details

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Data Type:	xbrli:stringItemType
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- Definition

The value (monetary amount) of the award the plaintiff seeks in the legal matter.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14326-108349

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 9
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14557-108349

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14435-108349

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

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- Details

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Namespace Prefix:
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- Details

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- Details

Name:	us-gaap_LitigationCaseAxis=lll_HVCAlkmaarMember
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Data Type:	na
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- Details

Name:	us-gaap_LossContingenciesByNatureOfContingencyAxis=lll_BusinessInterruptionMember
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Commitments and Contingencies (Details) € in Millions, $ in Millions			1 Months Ended	9 Months Ended	12 Months Ended
	Dec. 20, 2016 USD ($)	Jul. 23, 2014 EUR (€)	Aug. 31, 2014 Complaint	Sep. 29, 2017 USD ($)	Dec. 31, 2016 Complaint	Dec. 31, 2015 Complaint
Contingencies And Commitments [Line Items]
Recoveries from insurance contracts in connection with liabilities amount \| $				$ 0.0
EoTech Class Actions [Member]
Contingencies And Commitments [Line Items]
Number of putative class action complaints against entity \| Complaint					5	5
Securities Class Action [Member]
Contingencies And Commitments [Line Items]
Number of putative class action complaints against entity and officers \| Complaint			3
Settlement agreement amount \| $	$ 34.5
Property Damages [Member] \| HVC Alkmaar [Member]
Contingencies And Commitments [Line Items]
Claims for estimated damages \| €		€ 11
Business Interruption Damages [Member] \| HVC Alkmaar [Member]
Contingencies And Commitments [Line Items]
Claims for estimated damages \| €		€ 35