The Company and a Summary of Its Significant Accounting Policies - Summary of Disaggregation of Revenue by Segment and Products and Services (Detail) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Mar. 31, 2023
Disaggregation Of Revenue [Line Items]
Total revenues	$ 4,519,571	$ 4,283,758	$ 2,556,158
Product [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	1,293,795	1,279,164	954,126
Service [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	3,225,776	3,004,594	1,602,032
Operating Segments [Member] | Communication Services [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	3,298,485	3,141,540	1,704,775
Operating Segments [Member] | Communication Services [Member] | Product [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	276,139	343,028	269,126
Operating Segments [Member] | Communication Services [Member] | Service [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	3,022,346	2,798,512	1,435,649
Operating Segments [Member] | Defense and Advanced Technologies [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	1,221,086	1,142,218	851,383
Operating Segments [Member] | Defense and Advanced Technologies [Member] | Product [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	1,017,656	936,136	685,000
Operating Segments [Member] | Defense and Advanced Technologies [Member] | Service [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	$ 203,430	$ 206,082	$ 166,383