Basis of Presentation - Summary of Disaggregation of Revenue by Segment and Product and Services (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
Disaggregation Of Revenue [Line Items]
Total revenues	$ 554,694	$ 381,837	$ 1,511,037	$ 1,154,955
Product [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	301,865	175,957	800,429	523,858
Service [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	252,829	205,880	710,608	631,097
Operating Segments [Member] | Satellite Services [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	177,651	144,543	494,174	444,335
Operating Segments [Member] | Satellite Services [Member] | Product [Member]
Disaggregation Of Revenue [Line Items]
Total revenues		233		664
Operating Segments [Member] | Satellite Services [Member] | Service [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	177,651	144,310	494,174	443,671
Operating Segments [Member] | Commercial Networks [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	126,977	55,536	336,563	157,053
Operating Segments [Member] | Commercial Networks [Member] | Product [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	115,409	47,073	304,732	130,903
Operating Segments [Member] | Commercial Networks [Member] | Service [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	11,568	8,463	31,831	26,150
Operating Segments [Member] | Government Systems [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	250,066	181,758	680,300	553,567
Operating Segments [Member] | Government Systems [Member] | Product [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	186,456	128,651	495,697	392,291
Operating Segments [Member] | Government Systems [Member] | Service [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	$ 63,610	$ 53,107	$ 184,603	$ 161,276