Segment Information - Segment Assets (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Mar. 31, 2021
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	$ 5,992,860	$ 5,349,467
Operating Segments [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	1,150,643	702,771
Operating Segments [Member] | Satellite Services [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	451,194	64,048
Operating Segments [Member] | Commercial Networks [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	231,186	168,334
Operating Segments [Member] | Government Systems [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	468,263	470,389
Corporate, Non-Segment [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	$ 4,842,217	$ 4,646,696