Segment Information - Segment Assets (Detail) - USD ($) $ in Thousands	Sep. 30, 2019	Apr. 01, 2019	Mar. 31, 2019
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	$ 4,367,051	$ 4,242,149	$ 3,915,287
Operating Segments [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	700,807		677,529
Operating Segments [Member] | Satellite Services [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	80,715		85,907
Operating Segments [Member] | Commercial Networks [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	179,938		183,200
Operating Segments [Member] | Government Systems [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	440,154		408,422
Corporate, Non-Segment [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	$ 3,666,244		$ 3,237,758