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, 2018	Mar. 31, 2017	Mar. 31, 2016
Segment Reporting Information [Line Items]
Other acquired intangible assets, net	$ 31,862	$ 41,677
Goodwill	121,085	119,876
Amortization of acquired intangible assets	12,231	10,788	$ 16,438
Operating Segments [Member] | Satellite Services [Member]
Segment Reporting Information [Line Items]
Other acquired intangible assets, net	16,580	21,843
Goodwill	13,991	13,579
Amortization of acquired intangible assets	7,622	5,866	9,122
Operating Segments [Member] | Commercial Networks [Member]
Segment Reporting Information [Line Items]
Other acquired intangible assets, net	3,340	4,903
Goodwill	44,011	43,930
Amortization of acquired intangible assets	1,563	1,679	2,569
Operating Segments [Member] | Government Systems [Member]
Segment Reporting Information [Line Items]
Other acquired intangible assets, net	11,942	14,931
Goodwill	63,083	62,367
Amortization of acquired intangible assets	$ 3,046	$ 3,243	$ 4,747