Segment Information - Segment Revenues and Operating Profits (Losses) (Parenthetical) (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Segment Reporting Information [Line Items]
Product revenues	$ 187,235	$ 163,660	$ 347,911	$ 332,008
Income (loss) from operations	18,414	13,826	26,192	23,240
Operating Segments [Member]
Segment Reporting Information [Line Items]
Income (loss) from operations	20,691	18,413	30,982	32,637
Operating Segments [Member] | Satellite Services [Member]
Segment Reporting Information [Line Items]
Product revenues	6,782	6,376	13,467	12,652
Income (loss) from operations	32,550	21,036	63,417	38,077
Operating Segments [Member] | Implied License [Member] | Satellite Services [Member]
Segment Reporting Information [Line Items]
Product revenues	6,600	6,300	13,200	12,500
Income (loss) from operations	$ 6,600	$ 6,300	$ 13,200	$ 12,500