Accounting Standards Issued and Not Yet Implemented (Details)	Jun. 30, 2017
Accounting Standards Issued and Not Yet Implemented [Abstract]
Percentage of net sales generated from revenue that use the units-of-delivery method	20.00%

This element represents the percentage of net sales generated from revenue arrangements accounted for under the units-of-delivery method.

No definition available.

Name:	lll_NetSalesGeneratedFromRevenueAccountedForUnderTheUnitsOfDeliveryMethodPercent
Namespace Prefix:	lll_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant