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, 2019	Dec. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Mar. 31, 2019
Segment Reporting Information [Line Items]
Other acquired intangible assets, net	$ 16,271		$ 16,271		$ 22,301
Goodwill	121,745		121,745		121,719
Amortization of acquired intangible assets	1,856	$ 2,487	5,920	$ 7,375
Operating Segments [Member] | Satellite Services [Member]
Segment Reporting Information [Line Items]
Other acquired intangible assets, net	7,966		7,966		10,453
Goodwill	13,575		13,575		13,617
Amortization of acquired intangible assets	678	1,183	2,383	3,776
Operating Segments [Member] | Commercial Networks [Member]
Segment Reporting Information [Line Items]
Other acquired intangible assets, net	642		642		1,798
Goodwill	43,959		43,959		43,933
Amortization of acquired intangible assets	384	386	1,156	1,157
Operating Segments [Member] | Government Systems [Member]
Segment Reporting Information [Line Items]
Other acquired intangible assets, net	7,663		7,663		10,050
Goodwill	64,211		64,211		$ 64,169
Amortization of acquired intangible assets	$ 794	$ 918	$ 2,381	$ 2,442