Basis of Presentation - Summary of Disaggregation of Revenue by Segment and Product and Services (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Disaggregation Of Revenue [Line Items]
Total revenues	$ 517,474	$ 393,074	$ 956,343	$ 773,118
Product [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	280,435	181,783	498,564	347,901
Service [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	237,039	211,291	457,779	425,217
Operating Segments [Member] | Satellite Services [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	162,962	147,578	316,523	299,792
Operating Segments [Member] | Satellite Services [Member] | Product [Member]
Disaggregation Of Revenue [Line Items]
Total revenues		214		431
Operating Segments [Member] | Satellite Services [Member] | Service [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	162,962	147,364	316,523	299,361
Operating Segments [Member] | Commercial Networks [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	114,520	56,269	209,586	101,517
Operating Segments [Member] | Commercial Networks [Member] | Product [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	104,190	47,347	189,323	83,830
Operating Segments [Member] | Commercial Networks [Member] | Service [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	10,330	8,922	20,263	17,687
Operating Segments [Member] | Government Systems [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	239,992	189,227	430,234	371,809
Operating Segments [Member] | Government Systems [Member] | Product [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	176,245	134,222	309,241	263,640
Operating Segments [Member] | Government Systems [Member] | Service [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	$ 63,747	$ 55,005	$ 120,993	$ 108,169