Segment Information - Segment Revenues and Operating Profits (Losses) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016
Revenues:
Product revenues	$ 755,547	$ 713,936	$ 664,821
Service revenues	839,078	845,401	752,610
Total revenues	1,594,625	1,559,337	1,417,431
Operating profits (losses):
(Loss) income from operations	(92,187)	36,459	41,119
Amortization of acquired intangible assets	(12,231)	(10,788)	(16,438)
Operating Segments [Member]
Operating profits (losses):
(Loss) income from operations	(79,956)	47,247	57,557
Operating Segments [Member] | Satellite Services [Member]
Revenues:
Product revenues	664	27,711	25,606
Service revenues	588,623	601,936	533,628
Total revenues	589,287	629,647	559,234
Operating profits (losses):
(Loss) income from operations	12,018	131,085	81,830
Amortization of acquired intangible assets	(7,622)	(5,866)	(9,122)
Operating Segments [Member] | Commercial Networks [Member]
Revenues:
Product revenues	198,034	211,458	228,694
Service revenues	35,187	33,149	22,042
Total revenues	233,221	244,607	250,736
Operating profits (losses):
(Loss) income from operations	(229,105)	(180,496)	(111,339)
Amortization of acquired intangible assets	(1,563)	(1,679)	(2,569)
Operating Segments [Member] | Government Systems [Member]
Revenues:
Product revenues	556,849	474,767	410,521
Service revenues	215,268	210,316	196,940
Total revenues	772,117	685,083	607,461
Operating profits (losses):
(Loss) income from operations	137,131	96,658	87,066
Amortization of acquired intangible assets	(3,046)	(3,243)	(4,747)
Material Reconciling Items [Member]
Operating profits (losses):
Amortization of acquired intangible assets	$ (12,231)	$ (10,788)	$ (16,438)