Senior Notes and Other Long-Term Debt - Additional Information (Detail)	3 Months Ended
Jun. 30, 2018 USD ($) Installment	Sep. 30, 2017 USD ($)
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Credit Facility maximum borrowing capacity	$ 800,000,000
Maturity date of the Credit Facility	May 24, 2021
Credit Facility interest rate description	Borrowings under the Revolving Credit Facility bear interest, at the Company’s option, at either (1) the highest of the Federal Funds rate plus 0.50%, the Eurodollar rate plus 1.00%, or the administrative agent’s prime rate as announced from time to time, or (2) the Eurodollar rate, plus, in the case of each of (1) and (2), an applicable margin that is based on the Company’s total leverage ratio.
Weighted average effective interest rate	4.56%
Credit facility description	The Revolving Credit Facility contains financial covenants regarding a maximum total leverage ratio and a minimum interest coverage ratio. In addition, the Revolving Credit Facility contains covenants that restrict, among other things, the Company’s ability to sell assets, make investments and acquisitions, make capital expenditures, grant liens, pay dividends and make certain other restricted payments.
Principal amount of outstanding borrowings under the Credit Facility	$ 115,000,000
Borrowing availability under the Credit Facility	664,900,000
Ex-Im Credit Facility [Member]
Debt Instrument [Line Items]
Credit Facility maximum borrowing capacity	$ 362,400,000
Credit facility description	The Ex-Im Credit Facility contains financial covenants regarding Viasat’s maximum total leverage ratio and minimum interest coverage ratio. In addition, the Ex-Im Credit Facility contains covenants that restrict, among other things, the Company’s ability to sell assets, make investments and acquisitions, make capital expenditures, grant liens, pay dividends and make certain other restricted payments. Subsequent to quarter end, on July 17, 2018, the Ex-Im Credit Facility was amended in order to make conforming changes to the covenants to reflect the amendment made to the Revolving Credit Facility in May 2018.
Principal amount of outstanding borrowings under the Credit Facility	$ 339,800,000
Amount of qualified ViaSat-2 satellite costs limited to finance	$ 321,200,000
Percent of qualified ViaSat-2 expenses used to finance	85.00%
The maximum exposure fees under Ex-Im Credit Facility	$ 41,200,000
Interest rate on the outstanding borrowings	2.38%
Required number of installment repayments \| Installment	16
Debt maturity date	Oct. 15, 2025
Effective interest rate on the Ex-Im Credit Facility	4.60%
Ex-Im credit facility repayment commenced date	Apr. 15, 2018
Cumulative Ex-Im Credit Facility loan discount	$ 42,300,000
Exposure fees included in the principal	35,300,000
The exposure fees paid under Ex-Im Credit Facility borrowings	6,000,000
2025 Notes [Member]
Debt Instrument [Line Items]
Interest rate on the outstanding borrowings		5.625%
Principal amount of senior notes issued	$ 700,000,000	$ 700,000,000
2025 Notes [Member] \| Debt Instrument, Redemption, Other Period One [Member]
Debt Instrument [Line Items]
Redemption price percentage of Senior Notes	105.625%
Redemption description of Senior Notes	Prior to September 15, 2020, the Company may redeem up to 40% of the 2025 Notes at a redemption price of 105.625% of the principal amount thereof, plus accrued and unpaid interest, if any, thereon to the redemption date, from the net cash proceeds of specified equity offerings.
2025 Notes [Member] \| Debt Instrument, Redemption, Period One [Member]
Debt Instrument [Line Items]
Redemption price percentage of Senior Notes	100.00%
Redemption description of Senior Notes	The Company may also redeem the 2025 Notes prior to September 15, 2020, in whole or in part, at a redemption price equal to 100% of the principal amount thereof plus the applicable premium and any accrued and unpaid interest, if any, thereon to the redemption date. The applicable premium is calculated as the greater of: (i) 1.0% of the principal amount of such 2025 Notes and (ii) the excess, if any, of (a) the present value at such date of redemption of (1) the redemption price of such 2025 Notes on September 15, 2020 plus (2) all required interest payments due on such 2025 Notes through September 15, 2020 (excluding accrued but unpaid interest to the date of redemption), computed using a discount rate equal to the treasury rate (as defined under the indenture) plus 50 basis points, over (b) the then-outstanding principal amount of such 2025 Notes.
2025 Notes [Member] \| Debt Instrument, Redemption, Period Two [Member]
Debt Instrument [Line Items]
Redemption price percentage of Senior Notes	102.813%
Redemption description of Senior Notes	In whole or in part, at any time during the 12 months beginning on September 15, 2020 at a redemption price of 102.813%.
2025 Notes [Member] \| Debt Instrument, Redemption, Period Four [Member]
Debt Instrument [Line Items]
Redemption price percentage of Senior Notes	100.00%
Redemption description of Senior Notes	And at any time on or after September 15, 2022 at a redemption price of 100%, in each case plus accrued and unpaid interest, if any, thereon to the redemption date.
2025 Notes [Member] \| Debt Instrument, Redemption, Period Three [Member]
Debt Instrument [Line Items]
Redemption price percentage of Senior Notes	101.406%
Redemption description of Senior Notes	During the 12 months beginning on September 15, 2021 at a redemption price of 101.406%
2025 Notes [Member] \| Change of Control [Member]
Debt Instrument [Line Items]
Redemption price percentage of Senior Notes	101.00%
Redemption description of Senior Notes	In the event a change of control triggering event occurs (as defined in the indenture), each holder will have the right to require the Company to repurchase all or any part of such holder’s 2025 Notes at a purchase price in cash equal to 101% of the aggregate principal amount of the 2025 Notes repurchased, plus accrued and unpaid interest, if any, to the date of purchase (subject to the right of holders of record on the relevant record date to receive interest due on the relevant interest payment date).
Letter of Credit [Member]
Debt Instrument [Line Items]
Credit Facility maximum borrowing capacity	$ 150,000,000
Standby letters of credit outstanding amount	$ 20,100,000

Date the debt agreement requires the first payment to be made, in CCYY-MM-DD format.

Name:	us-gaap_DebtInstrumentDateOfFirstRequiredPayment1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28551-108399

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

+ Details

Name:	us-gaap_DebtInstrumentFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 6
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109500613&loc=SL6036836-161870

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28551-108399

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentInterestRateEffectivePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(2))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)
-URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258

+ Details

Name:	us-gaap_DebtInstrumentMaturityDate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Description of debt redemption features under terms of the debt agreement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
-Paragraph 3
-Subparagraph e
-URI http://asc.fasb.org/extlink&oid=75038535&loc=d3e64711-112823

+ Details

Name:	us-gaap_DebtInstrumentRedemptionDescription
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage price of original principal amount of debt at which debt can be redeemed by the issuer.

+ References

+ Details

Name:	us-gaap_DebtInstrumentRedemptionPricePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

No definition available.

+ Details

Name:	us-gaap_LettersOfCreditOutstandingAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

+ Details

Name:	us-gaap_LineOfCredit
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Description of the terms of a credit facility arrangement. Terms typically include interest rate, collateral required, guarantees required, repayment requirements, and restrictions on use of assets and activities of the entity.

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityDescription
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Date the credit facility terminates, in CCYY-MM-DD format.

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityExpirationDate1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Description of the interest rate for the amounts borrowed under the credit facility, including the terms and the method for determining the interest rate (for example, fixed or variable, LIBOR plus a percentage, increasing rate, timing of interest rate resets, remarketing provisions).

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityInterestRateDescription
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Weighted average interest rate of long-term debt outstanding calculated at point in time.

+ References

No definition available.

+ Details

Name:	us-gaap_LongtermDebtWeightedAverageInterestRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The cumulative amount of debt discount that was originally recognized at the issuance of the instrument before amortization.

+ References

No definition available.

+ Details

Name:	vsat_CumulativeDebtInstrumentUnamortizedDiscountBeforeAmortization
Namespace Prefix:	vsat_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Exposure fees included in the principal.

+ References

No definition available.

+ Details

Name:	vsat_ExposureFeesPrincipal
Namespace Prefix:	vsat_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The maximum percentage for a specific purpose other than for trade purchases that can be financed.

+ References

No definition available.

+ Details

Name:	vsat_LineOfCreditFacilityCapacityAvailableForSpecificPurposeOtherThanForTradePurchasesPercentage
Namespace Prefix:	vsat_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of exposure fees under the credit facility paid during the period.

+ References

No definition available.

+ Details

Name:	vsat_LineOfCreditFacilityExposureFeesPaid
Namespace Prefix:	vsat_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility, excluding financing fees.

+ References

No definition available.

+ Details

Name:	vsat_LineOfCreditFacilityMaximumBorrowingCapacityExcludingFinancingFees
Namespace Prefix:	vsat_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The maximum amount of exposure fees that could be incurred under the Credit Facility.

+ References

No definition available.

+ Details

Name:	vsat_LineOfCreditFacilityMaximumExposureFees
Namespace Prefix:	vsat_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Represents the required number of installments over which the borrowing must be repaid.

+ References

No definition available.

+ Details

Name:	vsat_LineOfCreditFacilityRequiredNumberOfRepayments
Namespace Prefix:	vsat_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_LineOfCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=vsat_ExportImportCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=vsat_TwoThousandAndTwentyFiveNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentRedemptionPeriodAxis=vsat_DebtInstrumentRedemptionOtherPeriodOneMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentRedemptionPeriodAxis=us-gaap_DebtInstrumentRedemptionPeriodOneMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentRedemptionPeriodAxis=us-gaap_DebtInstrumentRedemptionPeriodTwoMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentRedemptionPeriodAxis=us-gaap_DebtInstrumentRedemptionPeriodFourMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentRedemptionPeriodAxis=us-gaap_DebtInstrumentRedemptionPeriodThreeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentRedemptionPeriodAxis=vsat_ChangeOfControlMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_LetterOfCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: