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
	Jun. 30, 2019	Jun. 30, 2018	Mar. 31, 2019
Segment Reporting Information [Line Items]
Other acquired intangible assets, net	$ 20,354		$ 22,301
Goodwill	121,615		121,719
Amortization of acquired intangible assets	2,037	$ 2,453
Operating Segments [Member] | Satellite Services [Member]
Segment Reporting Information [Line Items]
Other acquired intangible assets, net	9,721		10,453
Goodwill	13,667		13,617
Amortization of acquired intangible assets	855	1,305
Operating Segments [Member] | Commercial Networks [Member]
Segment Reporting Information [Line Items]
Other acquired intangible assets, net	1,413		1,798
Goodwill	43,973		43,933
Amortization of acquired intangible assets	386	385
Operating Segments [Member] | Government Systems [Member]
Segment Reporting Information [Line Items]
Other acquired intangible assets, net	9,220		10,050
Goodwill	63,975		$ 64,169
Amortization of acquired intangible assets	$ 796	$ 763