Segment Information - Segment Revenues and Operating Profits (Losses) (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016
Revenues:
Product revenues	$ 175,957	$ 169,574	$ 523,858	$ 517,485
Service revenues	205,880	211,056	631,097	625,433
Total revenues	381,837	380,630	1,154,955	1,142,918
Operating profits (losses):
(Loss) income from operations	(25,326)	7,591	(59,136)	33,783
Amortization of acquired intangible assets	(3,177)	(2,775)	(9,757)	(7,565)
Operating Segments [Member]
Operating profits (losses):
(Loss) income from operations	(22,149)	10,366	(49,379)	41,348
Operating Segments [Member] | Satellite Services [Member]
Revenues:
Product revenues	233	7,114	664	20,581
Service revenues	144,310	152,978	443,671	448,188
Total revenues	144,543	160,092	444,335	468,769
Operating profits (losses):
(Loss) income from operations	1,681	34,846	33,140	98,263
Amortization of acquired intangible assets	(2,031)	(1,605)	(6,297)	(3,814)
Operating Segments [Member] | Commercial Networks [Member]
Revenues:
Product revenues	47,073	46,878	130,903	163,919
Service revenues	8,463	7,633	26,150	21,608
Total revenues	55,536	54,511	157,053	185,527
Operating profits (losses):
(Loss) income from operations	(53,505)	(48,598)	(179,007)	(127,997)
Amortization of acquired intangible assets	(385)	(411)	(1,178)	(1,267)
Operating Segments [Member] | Government Systems [Member]
Revenues:
Product revenues	128,651	115,582	392,291	332,985
Service revenues	53,107	50,445	161,276	155,637
Total revenues	181,758	166,027	553,567	488,622
Operating profits (losses):
(Loss) income from operations	29,675	24,118	96,488	71,082
Amortization of acquired intangible assets	(761)	(759)	(2,282)	(2,484)
Material Reconciling Items [Member]
Operating profits (losses):
Amortization of acquired intangible assets	$ (3,177)	$ (2,775)	$ (9,757)	$ (7,565)