Segment Information - Segment Revenues and Operating Profits (Losses) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Revenues:
Total revenues	$ 2,068,258	$ 1,594,625	$ 1,559,337
Operating profits (losses):
(Loss) income from operations	(60,620)	(92,187)	36,459
Amortization of acquired intangible assets	(9,655)	(12,231)	(10,788)
Product [Member]
Revenues:
Total revenues	1,092,691	755,547	713,936
Service [Member]
Revenues:
Total revenues	975,567	839,078	845,401
Operating Segments [Member]
Operating profits (losses):
(Loss) income from operations	(50,965)	(79,956)	47,247
Operating Segments [Member] | Satellite Services [Member]
Revenues:
Total revenues	684,205	589,287	629,647
Operating profits (losses):
(Loss) income from operations	(64,321)	12,018	131,085
Amortization of acquired intangible assets	(4,857)	(7,622)	(5,866)
Operating Segments [Member] | Satellite Services [Member] | Product [Member]
Revenues:
Total revenues		664	27,711
Operating Segments [Member] | Satellite Services [Member] | Service [Member]
Revenues:
Total revenues	684,205	588,623	601,936
Operating Segments [Member] | Commercial Networks [Member]
Revenues:
Total revenues	428,404	233,221	244,607
Operating profits (losses):
(Loss) income from operations	(166,613)	(229,105)	(180,496)
Amortization of acquired intangible assets	(1,542)	(1,563)	(1,679)
Operating Segments [Member] | Commercial Networks [Member] | Product [Member]
Revenues:
Total revenues	383,547	198,034	211,458
Operating Segments [Member] | Commercial Networks [Member] | Service [Member]
Revenues:
Total revenues	44,857	35,187	33,149
Operating Segments [Member] | Government Systems [Member]
Revenues:
Total revenues	955,649	772,117	685,083
Operating profits (losses):
(Loss) income from operations	179,969	137,131	96,658
Amortization of acquired intangible assets	(3,256)	(3,046)	(3,243)
Operating Segments [Member] | Government Systems [Member] | Product [Member]
Revenues:
Total revenues	709,144	556,849	474,767
Operating Segments [Member] | Government Systems [Member] | Service [Member]
Revenues:
Total revenues	246,505	215,268	210,316
Material Reconciling Items [Member]
Operating profits (losses):
Amortization of acquired intangible assets	$ (9,655)	$ (12,231)	$ (10,788)