The Company and a Summary of Its Significant Accounting Policies - Summary of Disaggregation of Revenue by Segment and Product and Services (Detail) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Disaggregation Of Revenue [Line Items]
Total revenues	$ 2,068,258	$ 1,594,625	$ 1,559,337
Product [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	1,092,691	755,547	713,936
Service [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	975,567	839,078	845,401
Operating Segments [Member] | Satellite Services [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	684,205	589,287	629,647
Operating Segments [Member] | Satellite Services [Member] | Product [Member]
Disaggregation Of Revenue [Line Items]
Total revenues		664	27,711
Operating Segments [Member] | Satellite Services [Member] | Service [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	684,205	588,623	601,936
Operating Segments [Member] | Commercial Networks [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	428,404	233,221	244,607
Operating Segments [Member] | Commercial Networks [Member] | Product [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	383,547	198,034	211,458
Operating Segments [Member] | Commercial Networks [Member] | Service [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	44,857	35,187	33,149
Operating Segments [Member] | Government Systems [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	955,649	772,117	685,083
Operating Segments [Member] | Government Systems [Member] | Product [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	709,144	556,849	474,767
Operating Segments [Member] | Government Systems [Member] | Service [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	$ 246,505	$ 215,268	$ 210,316