Changes in Carrying Amount of Goodwill (Detail) $ in Thousands	9 Months Ended
	Mar. 31, 2018 USD ($)
Goodwill [Roll Forward]
Beginning Balance	$ 380,846
Ending Balance	499,292
SMP
Goodwill [Roll Forward]
Beginning Balance	116,003
Ending Balance	119,741
AMS
Goodwill [Roll Forward]
Beginning Balance	217,956
Ending Balance	218,147
Mercury Defense Systems [Member]
Goodwill [Roll Forward]
Beginning Balance	46,887
Ending Balance	161,404
CES Creative Electronic Systems S.A.
Goodwill [Roll Forward]
Goodwill arising from the RTL acquisition	291
CES Creative Electronic Systems S.A. | SMP
Goodwill [Roll Forward]
Goodwill arising from the RTL acquisition	291
Delta
Goodwill [Roll Forward]
Goodwill arising from the RTL acquisition	191
Delta | AMS
Goodwill [Roll Forward]
Goodwill arising from the RTL acquisition	191
RTL
Goodwill [Roll Forward]
Goodwill arising from the RTL acquisition	3,447
RTL | SMP
Goodwill [Roll Forward]
Goodwill arising from the RTL acquisition	3,447
Themis
Goodwill [Roll Forward]
Goodwill arising from the RTL acquisition	114,517
Themis | Mercury Defense Systems [Member]
Goodwill [Roll Forward]
Goodwill arising from the RTL acquisition	$ 114,517