Basis of Presentation - Additional Information (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	Jun. 30, 2015
Company And Summary Of Significant Accounting Policies [Line Items]
Forward loss related to loss contracts	$ 1,600	$ 300	$ 2,000	$ 1,700
Defense contract audit agency completed cost audits			Contract costs on U.S. government contracts are subject to audit and review by the Defense Contracting Management Agency (DCMA), the Defense Contract Audit Agency (DCAA), and other U.S. government agencies, as well as negotiations with U.S. government representatives. The Company’s incurred cost audits by the DCAA have not been concluded for fiscal year 2016. As of September 30, 2016, the DCAA had completed its incurred cost audit for fiscal year 2004 and approved the Company’s incurred cost claims for fiscal years 2005 through 2015 without further audit. Although the Company has recorded contract revenues subsequent to fiscal year 2015 based upon an estimate of costs that the Company believes will be approved upon final audit or review, the Company does not know the outcome of any ongoing or future audits or reviews and adjustments, and if future adjustments exceed the Company’s estimates, its profitability would be adversely affected.
Advertising costs	800	2,900	$ 1,600	6,600
Capitalized interest expense	11,600	$ 7,100	21,800	$ 13,200
Total capitalized costs related to patents	3,200		3,200		$ 3,200
Total capitalized costs related to orbital slots and other licenses	15,400		15,400		15,400
Accumulated amortization of patents, orbital slots and other licenses	1,900		1,900		1,700
Capitalized debt issuance costs	6,100		$ 6,100
Minimum [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Property, equipment and satellites, estimated useful life (years)			2 years
Maximum [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Property, equipment and satellites, estimated useful life (years)			24 years
Property and Equipment, Net [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Property and equipment	1,143,156		$ 1,143,156		1,050,886
Accumulated depreciation and amortization	618,001		$ 618,001		563,976
CPE Leased Equipment [Member] | Minimum [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Property, equipment and satellites, estimated useful life (years)			4 years
CPE Leased Equipment [Member] | Maximum [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Property, equipment and satellites, estimated useful life (years)			5 years
CPE Leased Equipment [Member] | Property and Equipment, Net [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Property and equipment	266,811		$ 266,811		260,409
Accumulated depreciation and amortization	148,800		148,800		136,400
Engreen [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Purchase price of the acquisition						$ 5,300
Purchase price of the acquisition that has been withheld						$ 500
Unfavorable Regulatory Action [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
U.S. government contract-related reserves	$ 1,700		$ 1,700		$ 2,500