Composition of Certain Balance Sheet Captions - Composition of Certain Balance Sheet Captions (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Mar. 31, 2017
Accounts receivable, net:
Accounts receivable, Billed	$ 131,474	$ 145,626
Accounts receivable, Unbilled	98,888	119,565
Allowance for doubtful accounts	(2,325)	(1,470)
Accounts receivable, net	228,037	263,721
Inventories:
Raw materials	65,223	56,096
Work in process	41,777	25,820
Finished goods	75,059	81,285
Inventories	182,059	163,201
Prepaid expenses and other current assets:
Prepaid expenses	68,933	51,856
Other	7,423	5,980
Prepaid expenses and other current assets	76,356	57,836
Other acquired intangible assets, net:
Other acquired intangible assets, gross	218,096	215,091
Less: accumulated amortization	(184,234)	(173,414)
Other acquired intangible assets, net	33,862	41,677
Other assets:
Investment in unconsolidated affiliate	160,975	141,894
Deferred income taxes	205,735	134,764
Capitalized software costs, net	238,642	203,686
Patents, orbital slots and other licenses, net	16,200	16,500
Other	37,261	32,522
Other assets	658,813	529,366
Accrued liabilities:
Collections in excess of revenues and deferred revenues	77,371	76,682
Accrued employee compensation	48,608	41,691
Accrued vacation	35,381	33,214
Warranty reserve, current portion	5,514	7,796
Other	58,994	65,576
Accrued liabilities	225,868	224,959
Other liabilities:
Deferred revenue, long-term portion	79,407	4,617
Deferred rent, long-term portion	13,093	10,743
Warranty reserve, long-term portion	1,831	3,262
Satellite performance incentives obligation, long-term portion	18,445	19,164
Deferred income taxes, long-term	300	1,936
Other	4,762	3,000
Other liabilities	117,838	42,722
Technology [Member]
Other acquired intangible assets, net:
Other acquired intangible assets, gross	89,857	87,592
Contracts and Customer Relationships [Member]
Other acquired intangible assets, net:
Other acquired intangible assets, gross	103,613	103,034
Satellite Co-Location Rights [Member]
Other acquired intangible assets, net:
Other acquired intangible assets, gross	8,600	8,600
Trade Name [Member]
Other acquired intangible assets, net:
Other acquired intangible assets, gross	5,940	5,940
Other [Member]
Other acquired intangible assets, net:
Other acquired intangible assets, gross	10,086	9,925
Satellites, Net [Member]
Property and equipment, net:
Property and equipment	1,553,130	1,434,824
Less accumulated depreciation and amortization	(358,306)	(326,554)
Property and equipment, net	1,194,824	1,108,270
Property and Equipment, Net [Member]
Property and equipment, net:
Property and equipment	1,392,553	1,202,589
Less accumulated depreciation and amortization	(733,400)	(661,981)
Property and equipment, net	659,153	540,608
Satellites [Member] | Satellites, Net [Member]
Property and equipment, net:
Property and equipment	551,201	559,380
Capital Lease of Satellite Capacity - Anik F2 [Member] | Satellites, Net [Member]
Property and equipment, net:
Property and equipment	99,090	99,090
Construction in Progress [Member] | Satellites, Net [Member]
Property and equipment, net:
Property and equipment	902,839	776,354
Construction in Progress [Member] | Property and Equipment, Net [Member]
Property and equipment, net:
Property and equipment	154,615	116,902
Equipment and Software [Member] | Property and Equipment, Net [Member]
Property and equipment, net:
Property and equipment	773,410	679,008
CPE Leased Equipment [Member] | Property and Equipment, Net [Member]
Property and equipment, net:
Property and equipment	312,049	271,917
Less accumulated depreciation and amortization	(164,400)	(158,200)
Furniture and Fixtures [Member] | Property and Equipment, Net [Member]
Property and equipment, net:
Property and equipment	33,812	30,539
Leasehold Improvements [Member] | Property and Equipment, Net [Member]
Property and equipment, net:
Property and equipment	95,171	80,727
Building [Member] | Property and Equipment, Net [Member]
Property and equipment, net:
Property and equipment	8,923	8,923
Land [Member] | Property and Equipment, Net [Member]
Property and equipment, net:
Property and equipment	$ 14,573	$ 14,573