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	12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Segment Reporting Information [Line Items]
Other acquired intangible assets, net	$ 22,301	$ 31,862
Goodwill	121,719	121,085
Amortization of acquired intangible assets	9,655	12,231	$ 10,788
Operating Segments [Member] | Satellite Services [Member]
Segment Reporting Information [Line Items]
Other acquired intangible assets, net	10,453	16,580
Goodwill	13,617	13,991
Amortization of acquired intangible assets	4,857	7,622	5,866
Operating Segments [Member] | Commercial Networks [Member]
Segment Reporting Information [Line Items]
Other acquired intangible assets, net	1,798	3,340
Goodwill	43,933	44,011
Amortization of acquired intangible assets	1,542	1,563	1,679
Operating Segments [Member] | Government Systems [Member]
Segment Reporting Information [Line Items]
Other acquired intangible assets, net	10,050	11,942
Goodwill	64,169	63,083
Amortization of acquired intangible assets	$ 3,256	$ 3,046	$ 3,243