Basis of Presentation - Summary of Disaggregation of Revenue by Segment and Product and Services (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Disaggregation Of Revenue [Line Items]
Total revenues	$ 554,278	$ 592,256	$ 1,084,766	$ 1,129,293
Product [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	255,980	306,830	506,614	570,445
Service [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	298,298	285,426	578,152	558,848
Operating Segments [Member] | Satellite Services [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	215,887	205,717	417,871	402,532
Operating Segments [Member] | Satellite Services [Member] | Service [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	215,887	205,717	417,871	402,532
Operating Segments [Member] | Commercial Networks [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	78,860	88,008	146,022	167,020
Operating Segments [Member] | Commercial Networks [Member] | Product [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	66,751	74,143	121,870	139,044
Operating Segments [Member] | Commercial Networks [Member] | Service [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	12,109	13,865	24,152	27,976
Operating Segments [Member] | Government Systems [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	259,531	298,531	520,873	559,741
Operating Segments [Member] | Government Systems [Member] | Product [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	189,229	232,687	384,744	431,401
Operating Segments [Member] | Government Systems [Member] | Service [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	$ 70,302	$ 65,844	$ 136,129	$ 128,340