Property and Equipment - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2017
Property, Plant and Equipment [Line Items]
Increase in property and equipment	$ 9,021
Depreciation and amortization expense related to property and equipment	18,478	$ 16,273	$ 12,589
Computer equipment and software
Property, Plant and Equipment [Line Items]
Retirement of asset	$ 3,980	$ 611

Gross amount of long-lived physical assets disposed during the reporting period.

No definition available.

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Namespace Prefix:	mrcy_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The amount of expense recognized in the current period that reflects the allocation of the cost of tangible assets over the assets' useful lives. Includes production and non-production related depreciation.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3602-108585

+ Details

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Balance Type:	debit
Period Type:	duration

- Definition

Amount of increase (decrease) of long-lived, physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

+ References

No definition available.

+ Details

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- 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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- Details

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Namespace Prefix:
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Period Type: