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, 2018	Jun. 30, 2017	Mar. 31, 2018
Segment Reporting Information [Line Items]
Other acquired intangible assets, net	$ 28,558		$ 31,862
Goodwill	122,455		121,085
Amortization of acquired intangible assets	2,453	$ 3,260
Operating Segments [Member] | Satellite Services [Member]
Segment Reporting Information [Line Items]
Other acquired intangible assets, net	14,449		16,580
Goodwill	13,763		13,991
Amortization of acquired intangible assets	1,305	2,093
Operating Segments [Member] | Commercial Networks [Member]
Segment Reporting Information [Line Items]
Other acquired intangible assets, net	2,955		3,340
Goodwill	43,937		44,011
Amortization of acquired intangible assets	385	407
Operating Segments [Member] | Government Systems [Member]
Segment Reporting Information [Line Items]
Other acquired intangible assets, net	11,154		11,942
Goodwill	64,755		$ 63,083
Amortization of acquired intangible assets	$ 763	$ 760