Segment Information - Segment Revenues and Operating Profits (Losses) (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Revenues:
Total revenues	$ 701,354	$ 554,278	$ 1,366,214	$ 1,084,766
Operating profits (losses):
Income (loss) from operations	8,298	12,683	24,590	7,369
Amortization of acquired intangible assets	(7,399)	(1,300)	(13,328)	(2,858)
Product [Member]
Revenues:
Total revenues	308,666	255,980	601,930	506,614
Service [Member]
Revenues:
Total revenues	392,688	298,298	764,284	578,152
Operating Segments [Member]
Operating profits (losses):
Income (loss) from operations	15,697	13,983	37,918	10,227
Operating Segments [Member] | Satellite Services [Member]
Revenues:
Total revenues	300,110	215,887	574,227	417,871
Operating profits (losses):
Income (loss) from operations	17,046	11,483	29,559	9,626
Amortization of acquired intangible assets	(7,097)	(546)	(12,419)	(1,055)
Operating Segments [Member] | Satellite Services [Member] | Service [Member]
Revenues:
Total revenues	300,110	215,887	574,227	417,871
Operating Segments [Member] | Commercial Networks [Member]
Revenues:
Total revenues	134,806	78,860	253,402	146,022
Operating profits (losses):
Income (loss) from operations	(45,321)	(45,363)	(83,029)	(96,757)
Amortization of acquired intangible assets				(257)
Operating Segments [Member] | Commercial Networks [Member] | Product [Member]
Revenues:
Total revenues	118,935	66,751	220,466	121,870
Operating Segments [Member] | Commercial Networks [Member] | Service [Member]
Revenues:
Total revenues	15,871	12,109	32,936	24,152
Operating Segments [Member] | Government Systems [Member]
Revenues:
Total revenues	266,438	259,531	538,585	520,873
Operating profits (losses):
Income (loss) from operations	43,972	47,863	91,388	97,358
Amortization of acquired intangible assets	(302)	(754)	(909)	(1,546)
Operating Segments [Member] | Government Systems [Member] | Product [Member]
Revenues:
Total revenues	189,731	189,229	381,464	384,744
Operating Segments [Member] | Government Systems [Member] | Service [Member]
Revenues:
Total revenues	76,707	70,302	157,121	136,129
Material Reconciling Items [Member]
Operating profits (losses):
Amortization of acquired intangible assets	$ (7,399)	$ (1,300)	$ (13,328)	$ (2,858)