Senior Notes and Other Long-Term Debt - Additional Information (Detail)		3 Months Ended	6 Months Ended
	Sep. 21, 2017 USD ($)	Sep. 30, 2017 USD ($) Installment	Sep. 30, 2017 USD ($) Installment	Mar. 31, 2017 USD ($)
Debt Instrument [Line Items]
Loss on extinguishment of debt		$ (10,217,000)	$ (10,217,000)
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Credit Facility maximum borrowing capacity		800,000,000	$ 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.
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. As of September 30, 2017, the Revolving Credit Facility provided an $800.0 million revolving line of credit (including up to $150.0 million of letters of credit) with a maturity date of May 24, 2021.
Borrowing availability under the Credit Facility		769,900,000	$ 769,900,000
Principal amount of outstanding borrowings under the Credit Facility		0	0	$ 0
Letter of Credit [Member]
Debt Instrument [Line Items]
Credit Facility maximum borrowing capacity		150,000,000	150,000,000
Standby letters of credit outstanding amount		30,100,000	30,100,000
Ex-Im Credit Facility [Member]
Debt Instrument [Line Items]
Credit Facility maximum borrowing capacity		362,400,000	$ 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.
Amount of qualified ViaSat-2 satellite costs limited to finance		321,200,000	$ 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	$ 41,200,000
Interest rate on the outstanding borrowings		2.38%	2.38%
Required number of installment repayments | Installment		16	16
Debt maturity date			Oct. 15, 2025
Effective interest rate on the Ex-Im Credit Facility		4.60%	4.60%
Cumulative Ex-Im Credit Facility loan discount		$ 42,300,000	$ 42,300,000
Exposure fees included in the principal		35,300,000	35,300,000	29,500,000
The exposure fees paid under Ex-Im Credit Facility borrowings			6,000,000
2020 Notes [Member]
Debt Instrument [Line Items]
Principal amounts of Senior Notes issued	$ 575,000,000			$ 575,000,000
Loss on extinguishment of debt		(10,217,000)	(10,217,000)
Cash payment on extinguishment of debt		10,602,000	10,602,000
Non-cash gain (including unamortized premium, net of unamortized debt issuance costs)		400,000	400,000
2020 Notes [Member] | Tender Offer [Member]
Debt Instrument [Line Items]
Amount deposited to redeem debt	309,300,000
Aggregate principal amount	$ 298,200,000
2020 Notes [Member] | Redemption [Member]
Debt Instrument [Line Items]
Redemption price percentage of Senior Notes	101.719%
Amount deposited to redeem debt	$ 287,400,000
Aggregate principal amount	$ 276,800,000
2025 Notes [Member]
Debt Instrument [Line Items]
Interest rate on the outstanding borrowings	5.625%
Principal amounts of Senior Notes issued	$ 700,000,000	$ 700,000,000	$ 700,000,000
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			During the 12 months beginning on September 15, 2020 at a redemption price of 102.813%
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 trigger 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).
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, 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 2020 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.