The Company and a Summary of Its Significant Accounting Policies - Additional Information (Detail)	3 Months Ended		12 Months Ended			24 Months Ended
	Dec. 31, 2018	Sep. 30, 2018 USD ($)	Mar. 31, 2021 USD ($) Segment shares	Mar. 31, 2020 USD ($) shares	Mar. 31, 2019 USD ($) shares	Mar. 31, 2020 USD ($) shares
Company And Summary Of Significant Accounting Policies [Line Items]
Capitalized interest expense			$ 81,000,000.0	$ 54,100,000	$ 39,500,000
Property, equipment and satellites			4,834,919,000	4,101,634,000		$ 4,101,634,000
Accumulated depreciation and amortization			1,784,436,000	1,514,899,000		1,514,899,000
Proceeds from insurance claims on ViaSat-2 satellite				2,277,000	185,706,000	188,000,000.0
Total capitalized costs related to patents			3,500,000	3,300,000		3,300,000
Total capitalized costs related to orbital slots and other licenses			53,800,000	39,500,000		39,500,000
Accumulated amortization of patents, orbital slots and other licenses			4,400,000	3,700,000		3,700,000
Debt issuance costs capitalized			5,100,000	0	12,200,000
Capitalized costs, net, related to software developed for resale			237,100,000	242,741,000		242,741,000
Capitalized cost related to software development for resale			54,000,000.0	51,300,000
Amortization expense of capitalized software development costs			59,600,000	53,000,000.0	45,900,000
Goodwill and other intangible assets impairment			$ 0	0	0
Maximum warranty periods provided on limited warranty			5 years
Self-insurance liability			$ 6,900,000	$ 6,200,000		$ 6,200,000
Shares of common stock outstanding | shares			68,529,133	62,147,140		62,147,140
Repurchase and immediate retirement of treasury shares pursuant to vesting of certain RSU agreements			$ 13,676,000	$ 28,802,000	24,398,000
Other comprehensive income (loss) related to effects of foreign currency translation adjustments before tax			20,400,000	(12,800,000)	(11,800,000)
Foreign currency translation adjustments, net of tax			$ 15,851,000	(11,621,000)	(9,985,000)
Revenue, practical expedient, financing component			true
Remaining performance obligations			$ 2,300,000,000
Number of reportable segments | Segment			3
Decrease in unbilled accounts receivable			$ 4,900,000
Increase in collections in excess of revenues and deferred revenues			93,600,000
Collections in excess of revenues and deferred revenues, recognized revenue			98,600,000	93,100,000
Capitalized contract cost amortization and reduction of carrying value associated with contract termination			50,500,000	46,400,000	41,600,000
Advertising costs			12,000,000.0	25,800,000	$ 37,800,000
Prepaid Expenses and Other Current Assets [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Deferred customer contract costs			26,800,000	23,500,000		$ 23,500,000
Other Assets [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Deferred customer contract costs			57,800,000	53,500,000		53,500,000
Deferred Customer Contract Acquisition Costs [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Deferred customer contract costs			60,400,000	58,100,000		58,100,000
Deferred Customer Contract Fulfillment Costs [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Deferred customer contract costs			$ 24,200,000	$ 18,900,000		$ 18,900,000
Accounting Standards Update 2014-09 [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Revenue, practical expedient, incremental cost of obtaining contract [true false]			true	true
Accounting Standards Update 2016-13 [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Description of new accounting pronouncements			In June 2016, the Financial Accounting Standards Board (FASB) issued ASU 2016-13, Financial Instruments — Credit Losses (ASC 326). ASU 2016-13 requires credit losses on most financial assets measured at amortized cost and certain other instruments to be measured using an expected credit loss model (referred to as the current expected credit loss model). It also modifies the impairment model for available-for-sale debt securities and provides for a simplified accounting model for purchased financial assets with credit deterioration since their origination. In November 2018, the FASB issued ASU 2018-19, Codification Improvements to ASC 326, Financial Instruments — Credit Losses (ASC 326), which clarifies that impairment of receivables arising from operating leases should be accounted for in accordance with ASC 842, Leases. In April 2019, the FASB issued ASU 2019-04, Codification Improvements to ASC 326, Financial Instruments — Credit Losses, in May 2019, the FASB issued ASU 2019-05, Financial Instruments — Credit Losses (ASC 326) Targeted Relief, in November 2019, the FASB issued ASU 2019-11, Codification Improvements to ASC 326, Financial Instruments — Credit Losses, in February 2020, the FASB issued ASU 2020-02, Financial Instruments — Credit Losses (ASC 326) and Leases (ASC 842) Amendments to SEC Paragraphs Pursuant to SEC Staff Accounting Bulletin No. 119 and Update to SEC Section on Effective Date Related to ASU 2016-02, Leases (ASC 842) and in March 2020, the FASB issued ASU 2020-03, Codification Improvements to Financial Instruments. These recently issued ASUs do not change the core principle of the guidance in ASU 2016-13 but rather are intended to clarify and improve operability of certain topics included within ASU 2016-13. ASU 2018-19, ASU 2019-04, ASU 2019-05, ASU 2019-11, ASU 2020-02, and ASU 2020-03 have the same effective date and transition requirements as ASU 2016-13. The Company adopted the new guidance in the first quarter of fiscal year 2021 using the modified retrospective basis approach with application of the model to the Company’s accounts receivables. Under the new guidance, the Company is required to recognize estimated credit losses expected to occur over the estimated life or remaining contractual life of an asset using a broader range of information including past events, current conditions and consideration of supportable forecasts about future economic conditions. The adoption of this guidance had an insignificant impact on the Company’s consolidated financial statements and disclosures.
Accounting Standards Update 2018-13 [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Description of new accounting pronouncements			In August 2018, the FASB issued ASU 2018-13, Fair Value Measurement (ASC 820): Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement, which modifies the disclosure requirements for fair value measurements by removing, modifying, or adding certain disclosures. The Company adopted the new guidance in the first quarter of fiscal year 2021 and the guidance did not have a material impact on the Company’s consolidated financial statements and disclosures.
Accounting Standards Update 2019-12 [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Description of new accounting pronouncements			In December 2019, the FASB issued ASU 2019-12, Income Taxes (ASC 740): Simplifying the Accounting for Income Taxes, which is intended to simplify various areas related to accounting for income taxes. ASU 2019-12 removes certain exceptions to the general principles in ASC 740 and also clarifies and amends existing guidance to improve consistent application. ASU 2019-12 is effective for the Company beginning in fiscal year 2022. The Company is currently evaluating the impact of this standard on its consolidated financial statements and disclosures.
Accounting Standards Update 2020-01 [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Description of new accounting pronouncements			In January 2020, the FASB issued ASU 2020-01, Investments – Equity Securities (ASC 321), Investments – Equity Method and Joint Ventures (ASC 323) and Derivatives and Hedging (ASC 815). ASU 2020-01 clarifies the interaction of the accounting for equity securities under ASC 321 and investments accounted for under the equity method of accounting under ASC 323, and the accounting for certain forward contracts and purchased options accounted for under ASC 815. The new standard will become effective for the Company beginning in fiscal year 2022. The Company is currently evaluating the impact of this standard on its consolidated financial statements and disclosures.
Accounting Standards Update 2020-04 [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Description of new accounting pronouncements			In March 2020, the FASB issued ASU 2020-04, Reference Rate Reform (ASC 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting. ASU 2020-04 provides temporary optional guidance to ease the potential accounting burden associated with the transition away from reference rates (such as the London Interbank Offered Rate) that are expected to be discontinued. In January 2021, the FASB issued ASU 2021-01, Reference Rate Reform (Topic 848), which clarifies the scope and application of the guidance in ASU 2020-04. ASU 2021-01 clarifies that certain optional expedients and exceptions in ASU 2020-04 and Topic 848 for contract modifications and hedge accounting apply to derivatives that are affected by the discounting transition. The guidance in ASU 2020-04 and ASU 2021-01 are both effective upon issuance through December 31, 2022. The new guidance did not have a material impact on the Company’s consolidated financial statements and disclosures.
Accounting Standards Update 2020-06 [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Description of new accounting pronouncements			In August 2020, the FASB issued ASU 2020-06, Debt – Debt with Conversion and Other Options (ASC 470-20) and Derivatives and Hedging – Contracts in Entity’s Own Equity (Subtopic 815-40). ASU 2020-06 simplifies the accounting for convertible instruments by removing the beneficial conversion and cash conversion accounting models for convertible instruments and removes certain settlement conditions that are required for contracts to qualify for equity classification. This new standard also simplifies the diluted earnings per share calculations by requiring that an entity use the if-converted method for convertible instruments and requires that the effect of potential share settlement be included in diluted earnings per share calculations when an instrument may be settled in cash or shares. The new standard requires entities to provide expanded disclosures about the terms and features of convertible instruments, how the instruments have been reported in the entity’s financial statements, and information about events, conditions, and circumstances that can affect how to assess the amount or timing of an entity’s future cash flows related to those instruments. The new standard will become effective for the Company beginning in fiscal year 2023, with early adoption permitted, but no earlier than fiscal year 2022. The Company is currently evaluating the impact of this standard on its consolidated financial statements and disclosures.
Accounting Standards Update 2020-08 [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Description of new accounting pronouncements			In October 2020, the FASB issued ASU 2020-08, Codification Improvements to Subtopic 310-20, Receivables – Nonrefundable Fees and Other Costs. ASU 2020-08 clarifies that a company should reevaluate whether a callable debt security is within the scope of ASC paragraph 310-20-35-33 for each reporting period. The new standard will become effective for the Company beginning in fiscal year 2022. The Company is currently evaluating the impact of this standard on its consolidated financial statements and disclosures.
Accounting Standards Update 2020-09 [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Description of new accounting pronouncements			In October 2020, the FASB issued ASU 2020-09, Debt (ASC 740) to update the SEC guidance in the Codification related to the Final Rule (issued in March 2020). The SEC guidance in the Codification has updated financial disclosures about guarantors and issuers of guaranteed securities and affiliates whose securities collateralize a registrant’s securities. The final rules, among other things, allow omission of financial statements with respect to guaranteed securities when certain criteria are met and became effective on January 4, 2021. The guidance does not have a material impact on the Company’s consolidated financial statements and disclosures.
Accounting Standards Update 2020-10 [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Description of new accounting pronouncements			In October 2020, the FASB issued ASU 2020-10, Codification Improvements, which is related to a project by the FASB to facilitate codification updates for technical corrections, clarifications and other minor improvements that are not expected to have a significant effect on current accounting practice or create a significant administrative cost to most entities. The new standard contains amendments that affect a wide variety of topics in the ASC. The various amendments in this new standard will become effective for the Company beginning in fiscal year 2022, with early adoption permitted. The Company early adopted this guidance beginning in the fourth quarter of fiscal year 2021 and the guidance did not have a material impact on the Company’s consolidated financial statements and disclosures.
Funded Research and Development from Customer Contracts [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Percentage of revenue			23.00%	24.00%	19.00%
Operating Segments [Member] | Commercial Networks and Government Systems [Member] | Fixed-price Contract [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Percentage of revenue			89.00%	88.00%	90.00%
U.S. Government as an Individual Customer [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Percentage of revenue			26.00%	30.00%	30.00%
Other Customers [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Percentage of revenue			70.00%	70.00%	74.00%
Common Stock Held in Treasury [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Shares of common stock outstanding | shares			0	0		0
Purchase of treasury shares pursuant to vesting of certain RSU agreements | shares			376,884	385,604	427,088
Repurchase and immediate retirement of treasury shares pursuant to vesting of certain RSU agreements			$ 13,700,000	$ 28,800,000	$ 28,800,000
Common Stock [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Common stock issued based on the vesting terms of certain restricted stock unit agreements | shares			1,064,680	1,075,526	1,201,502
Indemnification Agreement [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Accrued reserves			$ 0	$ 0		$ 0
Unfavorable Regulatory Action [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Accrued reserves			$ 10,300,000	7,800,000		7,800,000
Minimum [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Property, equipment and satellites, estimated useful life (years)			2 years
Estimated useful life, years			2 years
Maximum [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Property, equipment and satellites, estimated useful life (years)			17 years
Estimated useful life, years			10 years
Maximum [Member] | Software Development Costs [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Estimated useful life, years			5 years
Internally Developed Software [Member] | Minimum [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Property, equipment and satellites, estimated useful life (years)			3 years
Internally Developed Software [Member] | Maximum [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Property, equipment and satellites, estimated useful life (years)			7 years
CPE Leased Equipment [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Property, equipment and satellites			$ 409,942,000	399,343,000		399,343,000
Accumulated depreciation and amortization			$ 193,700,000	165,700,000		165,700,000
CPE Leased Equipment [Member] | Minimum [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Property, equipment and satellites, estimated useful life (years)			4 years
CPE Leased Equipment [Member] | Maximum [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Property, equipment and satellites, estimated useful life (years)			5 years
Satellites [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Property, equipment and satellites			$ 969,952,000	$ 969,952,000		969,952,000
Reduction in property and equipment, net		$ 177,400,000
Satellites [Member] | Minimum [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Property, equipment and satellites, estimated useful life (years)			12 years
Satellites [Member] | Maximum [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Property, equipment and satellites, estimated useful life (years)			17 years
ViaSat-2 Satellite [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Estimated insurance claim receivable		$ 177,400,000
Proceeds from insurance claims on ViaSat-2 satellite						$ 188,000,000.0
Government Contracts Concentration Risk [Member] | Sales Revenue, Net [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Concentration risk, percentage			30.00%	30.00%	26.00%
Government Contracts Concentration Risk [Member] | Accounts Receivable [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Concentration risk, percentage			27.00%	35.00%
Customer Concentration Risk [Member] | Sales Revenue, Net [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Concentration risk, percentage			16.00%	18.00%	20.00%
Euro Retail Co [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Equity method investment ownership percentage	49.00%