Fair Value Measurements - Additional Information (Detail) - USD ($)	12 Months Ended
	Mar. 31, 2018	Sep. 30, 2017	Mar. 31, 2017
ViaSat-1 Satellite [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Satellite performance incentives obligation	$ 21,000,000
Satellite Performance Incentives Obligation [Member] | ViaSat-1 Satellite [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest on in-orbit satellite performance incentive obligation	7.00%
Period of in-orbit satellite performance incentive obligation	15 years
2025 Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Principal amount of senior notes issued	$ 700,000,000	$ 700,000,000
2020 Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Principal amount of senior notes issued		$ 575,000,000	$ 575,000,000
Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities measured at fair value on a recurring basis	0		96,000
Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities measured at fair value on a recurring basis			96,000
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Satellite Performance Incentives Obligation [Member] | ViaSat-1 Satellite [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Satellite performance incentives obligation	21,000,000		21,800,000
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | 2025 Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of long term debt	674,000,000
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Ex-Im Credit Facility [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of long term debt	$ 347,400,000		297,200,000
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | 2020 Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of long term debt			$ 587,900,000