Segment Information - Segment Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2024	Mar. 31, 2024
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	$ 15,600,351	$ 16,329,364
Operating Segments [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	4,926,094	5,160,985
Operating Segments [Member] | Communication Services [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	4,543,153	4,819,535
Operating Segments [Member] | Defense and Advanced Technologies [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	382,941	341,450
Corporate, Non-Segment [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	$ 10,674,257	$ 11,168,379