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, 2017	Jun. 30, 2016	Mar. 31, 2017
Segment Reporting Information [Line Items]
Other acquired intangible assets, net	$ 39,497		$ 41,677
Goodwill	120,419		119,876
Amortization of acquired intangible assets	3,260	$ 2,513
Operating Segments [Member] | Satellite Services [Member]
Segment Reporting Information [Line Items]
Other acquired intangible assets, net	20,810		21,843
Goodwill	13,815		13,579
Amortization of acquired intangible assets	2,093	1,104
Operating Segments [Member] | Commercial Networks [Member]
Segment Reporting Information [Line Items]
Other acquired intangible assets, net	4,495		4,903
Goodwill	44,003		43,930
Amortization of acquired intangible assets	407	445
Operating Segments [Member] | Government Systems [Member]
Segment Reporting Information [Line Items]
Other acquired intangible assets, net	14,192		14,931
Goodwill	62,601		$ 62,367
Amortization of acquired intangible assets	$ 760	$ 964