Changes in Carrying Amount of Goodwill (Detail) - USD ($) $ in Thousands	6 Months Ended	9 Months Ended
	Dec. 31, 2018	Mar. 31, 2019
Goodwill [Roll Forward]
Beginning Balance	$ 497,442	$ 497,442
Ending Balance		543,515
SMP
Goodwill [Roll Forward]
Beginning Balance	119,560	119,560
Ending Balance		142,383
AMS
Goodwill [Roll Forward]
Beginning Balance	218,147	218,147
Ending Balance		218,147
MDS
Goodwill [Roll Forward]
Beginning Balance	159,735	159,735
Ending Balance		182,985
Themis
Goodwill [Roll Forward]
Goodwill arising from acquisitions	139
Themis | SMP
Goodwill [Roll Forward]
Goodwill arising from acquisitions	0
Themis | AMS
Goodwill [Roll Forward]
Goodwill arising from acquisitions	0
Themis | MDS
Goodwill [Roll Forward]
Goodwill arising from acquisitions	139
Germane Systems
Goodwill [Roll Forward]
Goodwill arising from acquisitions	23,111
Germane Systems | SMP
Goodwill [Roll Forward]
Goodwill arising from acquisitions	0
Germane Systems | AMS
Goodwill [Roll Forward]
Goodwill arising from acquisitions	0
Germane Systems | MDS
Goodwill [Roll Forward]
Goodwill arising from acquisitions	$ 23,111
GECO Avionics, LLC
Goodwill [Roll Forward]
Goodwill arising from acquisitions		22,823
GECO Avionics, LLC | SMP
Goodwill [Roll Forward]
Goodwill arising from acquisitions		22,823
GECO Avionics, LLC | AMS
Goodwill [Roll Forward]
Goodwill arising from acquisitions		0
GECO Avionics, LLC | MDS
Goodwill [Roll Forward]
Goodwill arising from acquisitions		$ 0