Summary of Significant Accounting Policies - Additional Information (Detail)	3 Months Ended
Sep. 30, 2017	Sep. 30, 2016
Multiple Delivery Revenue [Member]
Significant Accounting Policies [Line Items]
Percentage Of revenue recognized	38.00%	35.00%

Percentage of total revenue recognized under multiple-deliverable arrangements during the reporting periods.

No definition available.

Name:	mrcy_PercentageOfRevenueRecognized
Namespace Prefix:	mrcy_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration