Composition of Certain Balance Sheet Captions - Composition of Certain Balance Sheet Captions (Parenthetical) (Detail)	12 Months Ended
	Mar. 31, 2018
Capital Lease of Satellite Capacity - Anik F2 [Member]
Schedule Of Composition Of Certain Balance Sheet Captions [Line Items]
Property, equipment and satellites, estimated useful life (years)	10 years
Furniture and Fixtures [Member]
Schedule Of Composition Of Certain Balance Sheet Captions [Line Items]
Property, equipment and satellites, estimated useful life (years)	7 years
Building [Member]
Schedule Of Composition Of Certain Balance Sheet Captions [Line Items]
Property, equipment and satellites, estimated useful life (years)	24 years
Minimum [Member]
Schedule Of Composition Of Certain Balance Sheet Captions [Line Items]
Property, equipment and satellites, estimated useful life (years)	2 years
Minimum [Member] | Satellites [Member]
Schedule Of Composition Of Certain Balance Sheet Captions [Line Items]
Property, equipment and satellites, estimated useful life (years)	10 years
Minimum [Member] | Equipment and Software [Member]
Schedule Of Composition Of Certain Balance Sheet Captions [Line Items]
Property, equipment and satellites, estimated useful life (years)	2 years
Minimum [Member] | CPE Leased Equipment [Member]
Schedule Of Composition Of Certain Balance Sheet Captions [Line Items]
Property, equipment and satellites, estimated useful life (years)	4 years
Minimum [Member] | Leasehold Improvements [Member]
Schedule Of Composition Of Certain Balance Sheet Captions [Line Items]
Property, equipment and satellites, estimated useful life (years)	2 years
Maximum [Member]
Schedule Of Composition Of Certain Balance Sheet Captions [Line Items]
Property, equipment and satellites, estimated useful life (years)	24 years
Maximum [Member] | Satellites [Member]
Schedule Of Composition Of Certain Balance Sheet Captions [Line Items]
Property, equipment and satellites, estimated useful life (years)	17 years
Maximum [Member] | Equipment and Software [Member]
Schedule Of Composition Of Certain Balance Sheet Captions [Line Items]
Property, equipment and satellites, estimated useful life (years)	7 years
Maximum [Member] | CPE Leased Equipment [Member]
Schedule Of Composition Of Certain Balance Sheet Captions [Line Items]
Property, equipment and satellites, estimated useful life (years)	5 years
Maximum [Member] | Leasehold Improvements [Member]
Schedule Of Composition Of Certain Balance Sheet Captions [Line Items]
Property, equipment and satellites, estimated useful life (years)	17 years