Segment Information - Segment Revenues and Operating Profits (Losses) (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Revenues:
Product revenues	$ 187,235	$ 163,660	$ 347,911	$ 332,008
Service revenues	211,923	189,670	414,377	365,700
Total revenues	399,158	353,330	762,288	697,708
Operating profits (losses):
Income from operations	18,414	13,826	26,192	23,240
Amortization of acquired intangible assets	(2,277)	(4,587)	(4,790)	(9,397)
Operating Segments [Member]
Operating profits (losses):
Income from operations	20,691	18,413	30,982	32,637
Operating Segments [Member] | Satellite Services [Member]
Revenues:
Product revenues	6,782	6,376	13,467	12,652
Service revenues	149,502	133,809	295,210	259,949
Total revenues	156,284	140,185	308,677	272,601
Operating profits (losses):
Income from operations	32,550	21,036	63,417	38,077
Amortization of acquired intangible assets	(1,105)	(2,765)	(2,209)	(5,530)
Operating Segments [Member] | Commercial Networks [Member]
Revenues:
Product revenues	58,445	61,983	117,041	123,494
Service revenues	7,018	4,387	13,975	9,631
Total revenues	65,463	66,370	131,016	133,125
Operating profits (losses):
Income from operations	(40,868)	(22,306)	(79,399)	(41,039)
Amortization of acquired intangible assets	(411)	(755)	(856)	(1,251)
Operating Segments [Member] | Government Systems [Member]
Revenues:
Product revenues	122,008	95,301	217,403	195,862
Service revenues	55,403	51,474	105,192	96,120
Total revenues	177,411	146,775	322,595	291,982
Operating profits (losses):
Income from operations	29,009	19,683	46,964	35,599
Amortization of acquired intangible assets	(761)	(1,067)	(1,725)	(2,616)
Material Reconciling Items [Member]
Operating profits (losses):
Amortization of acquired intangible assets	$ (2,277)	$ (4,587)	$ (4,790)	$ (9,397)