Segment Information - Segment Revenues and Operating Profits (Losses) (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Revenues:
Product revenues	$ 181,783	$ 187,235	$ 347,901	$ 347,911
Service revenues	211,291	211,923	425,217	414,377
Total revenues	393,074	399,158	773,118	762,288
Operating profits (losses):
(Loss) income from operations	(15,860)	18,414	(33,810)	26,192
Amortization of acquired intangible assets	(3,320)	(2,277)	(6,580)	(4,790)
Operating Segments [Member]
Operating profits (losses):
(Loss) income from operations	(12,540)	20,691	(27,230)	30,982
Operating Segments [Member] | Satellite Services [Member]
Revenues:
Product revenues	214	6,782	431	13,467
Service revenues	147,364	149,502	299,361	295,210
Total revenues	147,578	156,284	299,792	308,677
Operating profits (losses):
(Loss) income from operations	12,616	32,550	31,459	63,417
Amortization of acquired intangible assets	(2,173)	(1,105)	(4,267)	(2,209)
Operating Segments [Member] | Commercial Networks [Member]
Revenues:
Product revenues	47,347	58,445	83,830	117,041
Service revenues	8,922	7,018	17,687	13,975
Total revenues	56,269	65,463	101,517	131,016
Operating profits (losses):
(Loss) income from operations	(59,377)	(40,868)	(125,502)	(79,399)
Amortization of acquired intangible assets	(386)	(411)	(792)	(856)
Operating Segments [Member] | Government Systems [Member]
Revenues:
Product revenues	134,222	122,008	263,640	217,403
Service revenues	55,005	55,403	108,169	105,192
Total revenues	189,227	177,411	371,809	322,595
Operating profits (losses):
(Loss) income from operations	34,221	29,009	66,813	46,964
Amortization of acquired intangible assets	(761)	(761)	(1,521)	(1,725)
Material Reconciling Items [Member]
Operating profits (losses):
Amortization of acquired intangible assets	$ (3,320)	$ (2,277)	$ (6,580)	$ (4,790)