Segment Information - Segment Revenues and Operating Profits (Losses) (Parenthetical) (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Segment Reporting Information [Line Items]
Product revenues	$ 181,783	$ 187,235	$ 347,901	$ 347,911
Income (loss) from operations	(15,860)	18,414	(33,810)	26,192
Operating Segments [Member]
Segment Reporting Information [Line Items]
Income (loss) from operations	(12,540)	20,691	(27,230)	30,982
Operating Segments [Member] | Satellite Services [Member]
Segment Reporting Information [Line Items]
Product revenues	214	6,782	431	13,467
Income (loss) from operations	$ 12,616	32,550	$ 31,459	63,417
Operating Segments [Member] | Implied License [Member] | Satellite Services [Member]
Segment Reporting Information [Line Items]
Product revenues		6,600		13,200
Income (loss) from operations		$ 6,600		$ 13,200