Segment Information - Segment Revenues and Operating Profits (Losses) (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2016	Dec. 31, 2015
Revenues:
Product revenues	$ 169,574	$ 156,290	$ 517,485	$ 488,298
Service revenues	211,056	191,469	625,433	557,169
Total revenues	380,630	347,759	1,142,918	1,045,467
Operating profits (losses):
Income from operations	7,591	10,385	33,783	33,625
Amortization of acquired intangible assets	(2,775)	(4,261)	(7,565)	(13,658)
Operating Segments [Member]
Operating profits (losses):
Income from operations	10,366	14,646	41,348	47,283
Operating Segments [Member] | Satellite Services [Member]
Revenues:
Product revenues	7,114	6,453	20,581	19,105
Service revenues	152,978	134,751	448,188	394,700
Total revenues	160,092	141,204	468,769	413,805
Operating profits (losses):
Income from operations	34,846	21,772	98,263	59,849
Amortization of acquired intangible assets	(1,605)	(2,488)	(3,814)	(8,018)
Operating Segments [Member] | Commercial Networks [Member]
Revenues:
Product revenues	46,878	49,617	163,919	173,111
Service revenues	7,633	5,809	21,608	15,440
Total revenues	54,511	55,426	185,527	188,551
Operating profits (losses):
Income from operations	(48,598)	(29,889)	(127,997)	(70,928)
Amortization of acquired intangible assets	(411)	(706)	(1,267)	(1,957)
Operating Segments [Member] | Government Systems [Member]
Revenues:
Product revenues	115,582	100,220	332,985	296,082
Service revenues	50,445	50,909	155,637	147,029
Total revenues	166,027	151,129	488,622	443,111
Operating profits (losses):
Income from operations	24,118	22,763	71,082	58,362
Amortization of acquired intangible assets	(759)	(1,067)	(2,484)	(3,683)
Material Reconciling Items [Member]
Operating profits (losses):
Amortization of acquired intangible assets	$ (2,775)	$ (4,261)	$ (7,565)	$ (13,658)