Property and Equipment - Unamortized Deferred Gain (Detail) - USD ($) $ in Thousands	Jun. 30, 2016	Jun. 30, 2015
Property, Plant and Equipment [Abstract]
Current portion	$ 929	$ 1,156
Non-current portion	0	929
Total unamortized deferred gain	$ 929	$ 2,085

The current portion of the gain that will be recorded as income or a reduction in rent expense in future periods.

No definition available.

Name:	mrcy_SaleLeasebackTransactionDeferredGainCurrentPortion
Namespace Prefix:	mrcy_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant