Segment Information - Segment Assets (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Mar. 31, 2018
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	$ 3,915,287	$ 3,414,109
Operating Segments [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	677,529	615,728
Operating Segments [Member] | Satellite Services [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	85,907	66,830
Operating Segments [Member] | Commercial Networks [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	183,200	211,447
Operating Segments [Member] | Government Systems [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	408,422	337,451
Corporate, Non-Segment [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	$ 3,237,758	$ 2,798,381