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, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Mar. 31, 2019
Segment Reporting Information [Line Items]
Other acquired intangible assets, net	$ 17,967		$ 17,967		$ 22,301
Goodwill	121,223		121,223		121,719
Amortization of acquired intangible assets	2,027	$ 2,435	4,064	$ 4,888
Operating Segments [Member] | Satellite Services [Member]
Segment Reporting Information [Line Items]
Other acquired intangible assets, net	8,550		8,550		10,453
Goodwill	13,535		13,535		13,617
Amortization of acquired intangible assets	850	1,289	1,705	2,593
Operating Segments [Member] | Commercial Networks [Member]
Segment Reporting Information [Line Items]
Other acquired intangible assets, net	1,028		1,028		1,798
Goodwill	43,945		43,945		43,933
Amortization of acquired intangible assets	386	385	772	771
Operating Segments [Member] | Government Systems [Member]
Segment Reporting Information [Line Items]
Other acquired intangible assets, net	8,389		8,389		10,050
Goodwill	63,743		63,743		$ 64,169
Amortization of acquired intangible assets	$ 791	$ 761	$ 1,587	$ 1,524