Segment Information - Segment Revenues and Operating Profits (Losses) (Parenthetical) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016
Segment Reporting Information [Line Items]
Product revenues	$ 755,547	$ 713,936	$ 664,821
Income (loss) from operations	(92,187)	$ 36,459	$ 41,119
TrellisWare [Member]
Segment Reporting Information [Line Items]
Minority interest ownership percentage by parent		52.00%	52.00%
Operating Segments [Member]
Segment Reporting Information [Line Items]
Income (loss) from operations	(79,956)	$ 47,247	$ 57,557
Operating Segments [Member] | Satellite Services [Member]
Segment Reporting Information [Line Items]
Product revenues	664	27,711	25,606
Income (loss) from operations	12,018	131,085	81,830
Operating Segments [Member] | Government Systems [Member]
Segment Reporting Information [Line Items]
Product revenues	556,849	474,767	410,521
Income (loss) from operations	$ 137,131	96,658	87,066
Uncharacterized damages and penalties		11,800
Operating Segments [Member] | Implied License [Member] | Satellite Services [Member]
Segment Reporting Information [Line Items]
Product revenues		26,800	25,300
Income (loss) from operations		$ 26,800	$ 25,300