Segment Information - Other Acquired Intangible Assets, Net and Goodwill Included in Segment Assets and Amortization of Acquired Intangible Assets by Segment (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Mar. 31, 2020
Segment Reporting Information [Line Items]
Other acquired intangible assets, net	$ 12,030		$ 12,030		$ 14,439
Goodwill	121,765		121,765		121,197
Amortization of acquired intangible assets	1,300	$ 2,027	2,858	$ 4,064
Operating Segments [Member] | Satellite Services [Member]
Segment Reporting Information [Line Items]
Other acquired intangible assets, net	6,733		6,733		7,368
Goodwill	13,758		13,758		13,489
Amortization of acquired intangible assets	546	850	1,055	1,705
Operating Segments [Member] | Commercial Networks [Member]
Segment Reporting Information [Line Items]
Other acquired intangible assets, net					257
Goodwill	44,063		44,063		43,981
Amortization of acquired intangible assets		386	257	772
Operating Segments [Member] | Government Systems [Member]
Segment Reporting Information [Line Items]
Other acquired intangible assets, net	5,297		5,297		6,814
Goodwill	63,944		63,944		$ 63,727
Amortization of acquired intangible assets	$ 754	$ 791	$ 1,546	$ 1,587