Segment Information - Segment Revenues and Operating Profits (Losses) (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2019	Dec. 31, 2018
Revenues:
Total revenues	$ 588,224	$ 554,694	$ 1,717,517	$ 1,511,037
Operating profits (losses):
Income (loss) from operations	13,969	6,007	24,329	(70,043)
Amortization of acquired intangible assets	(1,856)	(2,487)	(5,920)	(7,375)
Product [Member]
Revenues:
Total revenues	303,090	301,865	873,535	800,429
Service [Member]
Revenues:
Total revenues	285,134	252,829	843,982	710,608
Operating Segments [Member]
Operating profits (losses):
Income (loss) from operations	15,825	8,494	30,249	(62,668)
Operating Segments [Member] | Satellite Services [Member]
Revenues:
Total revenues	211,700	177,651	614,232	494,174
Operating profits (losses):
Income (loss) from operations	3,600	(10,196)	6,648	(64,971)
Amortization of acquired intangible assets	(678)	(1,183)	(2,383)	(3,776)
Operating Segments [Member] | Satellite Services [Member] | Service [Member]
Revenues:
Total revenues	211,700	177,651	614,232	494,174
Operating Segments [Member] | Commercial Networks [Member]
Revenues:
Total revenues	84,726	126,977	251,746	336,563
Operating profits (losses):
Income (loss) from operations	(46,917)	(31,219)	(143,559)	(117,424)
Amortization of acquired intangible assets	(384)	(386)	(1,156)	(1,157)
Operating Segments [Member] | Commercial Networks [Member] | Product [Member]
Revenues:
Total revenues	73,182	115,409	212,226	304,732
Operating Segments [Member] | Commercial Networks [Member] | Service [Member]
Revenues:
Total revenues	11,544	11,568	39,520	31,831
Operating Segments [Member] | Government Systems [Member]
Revenues:
Total revenues	291,798	250,066	851,539	680,300
Operating profits (losses):
Income (loss) from operations	59,142	49,909	167,160	119,727
Amortization of acquired intangible assets	(794)	(918)	(2,381)	(2,442)
Operating Segments [Member] | Government Systems [Member] | Product [Member]
Revenues:
Total revenues	229,908	186,456	661,309	495,697
Operating Segments [Member] | Government Systems [Member] | Service [Member]
Revenues:
Total revenues	61,890	63,610	190,230	184,603
Material Reconciling Items [Member]
Operating profits (losses):
Amortization of acquired intangible assets	$ (1,856)	$ (2,487)	$ (5,920)	$ (7,375)