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, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Mar. 31, 2016
Segment Reporting Information [Line Items]
Other acquired intangible assets, net	$ 28,742		$ 28,742		$ 33,604
Goodwill	116,404		116,404		117,040
Amortization of acquired intangible assets	2,277	$ 4,587	4,790	$ 9,397
Operating Segments [Member] | Satellite Services [Member]
Segment Reporting Information [Line Items]
Other acquired intangible assets, net	6,541		6,541		8,751
Goodwill	9,809		9,809		9,809
Amortization of acquired intangible assets	1,105	2,765	2,209	5,530
Operating Segments [Member] | Commercial Networks [Member]
Segment Reporting Information [Line Items]
Other acquired intangible assets, net	5,726		5,726		6,581
Goodwill	43,977		43,977		43,990
Amortization of acquired intangible assets	411	755	856	1,251
Operating Segments [Member] | Government Systems [Member]
Segment Reporting Information [Line Items]
Other acquired intangible assets, net	16,475		16,475		18,272
Goodwill	62,618		62,618		$ 63,241
Amortization of acquired intangible assets	$ 761	$ 1,067	$ 1,725	$ 2,616