Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Millions		1 Months Ended		12 Months Ended
	Sep. 30, 2017	Apr. 30, 2017	May 31, 2013	Mar. 31, 2017	Mar. 31, 2016
Long-term Purchase Commitment [Line Items]
Loss contingency impact to net income attributable to ViaSat, Inc. stockholders				$ 4.0
Loss contingency impact to net (loss) income attributable to noncontrolling interests, net of tax				3.7
TrellisWare [Member]
Long-term Purchase Commitment [Line Items]
Minority interest ownership percentage by parent					52.00%
Operating Segments [Member] | Government Systems [Member]
Long-term Purchase Commitment [Line Items]
Accrued total loss contingency				11.8
Accrued loss contingency in uncharacterized damages				11.4
Accrued loss contingency in penalties				0.4
Accrued Liabilities [Member]
Long-term Purchase Commitment [Line Items]
Accrued total loss contingency	$ 8.8
Other Long Term Liabilities [Member]
Long-term Purchase Commitment [Line Items]
Accrued total loss contingency	3.0
Unfavorable Regulatory Action [Member]
Long-term Purchase Commitment [Line Items]
U.S. government contract-related reserves	1.3			$ 1.8
Satellite - ViaSat-2 [Member] | Capital Addition [Member]
Long-term Purchase Commitment [Line Items]
Commitment amount			$ 358.0
Satellite - ViaSat-2 [Member] | Satellite Performance Incentives Obligation [Member]
Long-term Purchase Commitment [Line Items]
Commitment amount		$ 21.0
Period of in-orbit satellite performance incentive payments		9 years
ViaSat-3 Class Satellites [Member] | Capital Addition [Member]
Long-term Purchase Commitment [Line Items]
Commitment amount	$ 379.5