Segment Information - Segment Revenues and Operating Profits (Losses) (Detail) - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Revenues:
Total revenues	$ 438,869	$ 380,044
Operating profits (losses):
Loss from operations	(54,479)	(17,950)
Amortization of acquired intangible assets	(2,453)	(3,260)
Product [Member]
Revenues:
Total revenues	218,129	166,118
Service [Member]
Revenues:
Total revenues	220,740	213,926
Operating Segments [Member]
Operating profits (losses):
Loss from operations	(52,026)	(14,690)
Operating Segments [Member] | Satellite Services [Member]
Revenues:
Total revenues	153,561	152,214
Operating profits (losses):
Loss from operations	(29,936)	18,843
Amortization of acquired intangible assets	(1,305)	(2,093)
Operating Segments [Member] | Satellite Services [Member] | Product [Member]
Revenues:
Total revenues		217
Operating Segments [Member] | Satellite Services [Member] | Service [Member]
Revenues:
Total revenues	153,561	151,997
Operating Segments [Member] | Commercial Networks [Member]
Revenues:
Total revenues	95,066	45,248
Operating profits (losses):
Loss from operations	(47,008)	(66,125)
Amortization of acquired intangible assets	(385)	(407)
Operating Segments [Member] | Commercial Networks [Member] | Product [Member]
Revenues:
Total revenues	85,133	36,483
Operating Segments [Member] | Commercial Networks [Member] | Service [Member]
Revenues:
Total revenues	9,933	8,765
Operating Segments [Member] | Government Systems [Member]
Revenues:
Total revenues	190,242	182,582
Operating profits (losses):
Loss from operations	24,918	32,592
Amortization of acquired intangible assets	(763)	(760)
Operating Segments [Member] | Government Systems [Member] | Product [Member]
Revenues:
Total revenues	132,996	129,418
Operating Segments [Member] | Government Systems [Member] | Service [Member]
Revenues:
Total revenues	57,246	53,164
Material Reconciling Items [Member]
Operating profits (losses):
Amortization of acquired intangible assets	$ (2,453)	$ (3,260)