Segment Information - Segment Revenues and Operating Profits (Losses) (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2020	Dec. 31, 2019
Revenues:
Total revenues	$ 575,559	$ 588,224	$ 1,660,325	$ 1,717,517
Operating profits (losses):
Income (loss) from operations	21,760	13,969	29,129	24,329
Amortization of acquired intangible assets	(1,313)	(1,856)	(4,171)	(5,920)
Product [Member]
Revenues:
Total revenues	266,514	303,090	773,128	873,535
Service [Member]
Revenues:
Total revenues	309,045	285,134	887,197	843,982
Operating Segments [Member]
Operating profits (losses):
Income (loss) from operations	23,073	15,825	33,300	30,249
Operating Segments [Member] | Satellite Services [Member]
Revenues:
Total revenues	220,789	211,700	638,660	614,232
Operating profits (losses):
Income (loss) from operations	11,457	3,600	21,083	6,648
Amortization of acquired intangible assets	(557)	(678)	(1,612)	(2,383)
Operating Segments [Member] | Satellite Services [Member] | Service [Member]
Revenues:
Total revenues	220,789	211,700	638,660	614,232
Operating Segments [Member] | Commercial Networks [Member]
Revenues:
Total revenues	90,099	84,726	236,121	251,746
Operating profits (losses):
Income (loss) from operations	(39,028)	(46,917)	(135,785)	(143,559)
Amortization of acquired intangible assets		(384)	(257)	(1,156)
Operating Segments [Member] | Commercial Networks [Member] | Product [Member]
Revenues:
Total revenues	75,690	73,182	197,560	212,226
Operating Segments [Member] | Commercial Networks [Member] | Service [Member]
Revenues:
Total revenues	14,409	11,544	38,561	39,520
Operating Segments [Member] | Government Systems [Member]
Revenues:
Total revenues	264,671	291,798	785,544	851,539
Operating profits (losses):
Income (loss) from operations	50,644	59,142	148,002	167,160
Amortization of acquired intangible assets	(756)	(794)	(2,302)	(2,381)
Operating Segments [Member] | Government Systems [Member] | Product [Member]
Revenues:
Total revenues	190,824	229,908	575,568	661,309
Operating Segments [Member] | Government Systems [Member] | Service [Member]
Revenues:
Total revenues	73,847	61,890	209,976	190,230
Material Reconciling Items [Member]
Operating profits (losses):
Amortization of acquired intangible assets	$ (1,313)	$ (1,856)	$ (4,171)	$ (5,920)