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		9 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Mar. 31, 2020
Segment Reporting Information [Line Items]
Other acquired intangible assets, net	$ 11,079		$ 11,079		$ 14,439
Goodwill	122,448		122,448		121,197
Amortization of acquired intangible assets	1,313	$ 1,856	4,171	$ 5,920
Operating Segments [Member] | Satellite Services [Member]
Segment Reporting Information [Line Items]
Other acquired intangible assets, net	6,499		6,499		7,368
Goodwill	13,955		13,955		13,489
Amortization of acquired intangible assets	557	678	1,612	2,383
Operating Segments [Member] | Commercial Networks [Member]
Segment Reporting Information [Line Items]
Other acquired intangible assets, net					257
Goodwill	44,146		44,146		43,981
Amortization of acquired intangible assets		384	257	1,156
Operating Segments [Member] | Government Systems [Member]
Segment Reporting Information [Line Items]
Other acquired intangible assets, net	4,580		4,580		6,814
Goodwill	64,347		64,347		$ 63,727
Amortization of acquired intangible assets	$ 756	$ 794	$ 2,302	$ 2,381