The Company and a Summary of Its Significant Accounting Policies - Additional Information (Detail)	3 Months Ended				12 Months Ended
	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Dec. 31, 2018	Sep. 30, 2018 USD ($)	Mar. 31, 2020 USD ($) Segment shares	Mar. 31, 2019 USD ($) shares	Mar. 31, 2018 USD ($) shares
Company And Summary Of Significant Accounting Policies [Line Items]
Capitalized interest expense					$ 54,100,000	$ 39,500,000	$ 58,900,000
Property, equipment and satellites					4,101,634,000	3,419,456,000
Accumulated depreciation and amortization					1,514,899,000	1,294,166,000
Proceeds from insurance claims on ViaSat-2 satellite	$ 2,300,000				$ 2,277,000	185,706,000
Lease, practical expedients, package [true false]					true
Total capitalized costs related to patents					$ 3,300,000	3,200,000
Total capitalized costs related to orbital slots and other licenses					39,500,000	22,900,000
Accumulated amortization of patents, orbital slots and other licenses					3,700,000	3,000,000.0
Debt issuance costs capitalized					0	12,200,000	9,800,000
Capitalized costs, net, related to software developed for resale					242,741,000	244,368,000
Capitalized cost related to software development for resale					51,300,000	43,500,000
Amortization expense of capitalized software development costs					53,000,000.0	45,900,000	32,500,000
Goodwill and other intangible assets impairment					$ 0	0	0
Maximum warranty periods provided on limited warranty					5 years
Self-insurance liability					$ 6,200,000	$ 5,400,000
Shares of common stock outstanding | shares					62,147,140	60,550,093
Repurchase and immediate retirement of treasury shares pursuant to vesting of certain RSU agreements					$ 28,802,000	$ 24,398,000	24,206,000
Other comprehensive income (loss) related to effects of foreign currency translation adjustments before tax					(12,800,000)	(11,800,000)	22,800,000
Foreign currency translation adjustments, net of tax					$ (11,621,000)	(9,985,000)	15,785,000
Revenue, practical expedient, financing component					true
Remaining performance obligations					$ 1,900,000,000
Number of reportable segments | Segment					3
Decrease in unbilled accounts receivable					$ 8,100,000
Decrease in collections in excess of revenues and deferred revenues					(2,500,000)
Collections in excess of revenues and deferred revenues, recognized revenue					93,100,000
Capitalized contract cost amortization and reduction of carrying value associated with contract termination					46,400,000	41,600,000
Advertising costs					25,800,000	37,800,000	$ 14,400,000
Prepaid Expenses and Other Current Assets [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Deferred customer contract costs					23,500,000	20,600,000
Other Assets [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Deferred customer contract costs					53,500,000	41,300,000
Deferred Customer Contract Acquisition Costs [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Deferred customer contract costs					58,100,000	52,000,000.0
Deferred Customer Contract Fulfillment Costs [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Deferred customer contract costs					$ 18,900,000	$ 9,900,000
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 2016-02 [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Description of new accounting pronouncements					In February 2016, the Financial Accounting Standards Board (FASB) issued ASU 2016-02, Leases (ASC 842). ASU 2016-02 requires lessees to recognize most leases on their balance sheets as lease liabilities with corresponding right-of-use assets and eliminates certain real estate-specific provisions. In January 2018, the FASB issued ASU 2018-01, Leases (ASC 842). ASU 2018-01 permits an entity to elect an optional transition practical expedient to not evaluate land easements that exist or expired before the entity’s adoption of ASC 842 and that were not previously accounted for as leases under ASC 840. In July 2018, the FASB issued ASU 2018-10, Codification Improvements to ASC 842, Leases, which was issued to provide more detailed guidance and additional clarification for implementing ASU 2016-02. In July 2018, the FASB issued ASU 2018-11, Leases (ASC 842): Targeted Improvements, which provides an additional (and optional) transition method whereby the new lease standard is applied at the adoption date and recognized as an adjustment to retained earnings. In December 2018, the FASB issued ASU 2018-20, Leases (ASC 842): Narrow-Scope Improvements for Lessors, and in March 2019, the FASB issued ASU 2019-01 (ASC 842): Codification Improvements, both of which provide certain amendments that affect narrow aspects of the guidance issued in ASU 2016-02. The Company adopted the new guidance using the optional transition method in the first quarter of fiscal year 2020. Therefore, the periods prior to the effective date of adoption continue to be reported under the current authoritative guidance for leases (ASC 840). The adoption of this guidance materially impacted the Company’s consolidated balance sheet upon adoption due to the recognition of lease liabilities and right-of-use assets. The new guidance did not have a material impact on the Company’s consolidated statements of operations and comprehensive income (loss) or consolidated statements of cash flows
Accounting Standards Update 2016-13 [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Description of new accounting pronouncements					In June 2016, the 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, and in November 2019, the FASB issued ASU 2019-11, Codification Improvements to ASC 326, Financial Instruments – Credit Losses. 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 and ASU 2019-11 have the same effective date and transition requirements as ASU 2016-13. The new guidance will become effective for the Company beginning in fiscal year 2021, with early adoption permitted. The new guidance is required to be applied on a modified-retrospective basis. The Company is currently evaluating the impact of this standard on its consolidated financial statements and disclosures.
Accounting Standards Update 2017-04 [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Description of new accounting pronouncements					In January 2017, the FASB issued ASU 2017-04, Intangibles — Goodwill and Other: Simplifying the Test for Goodwill Impairment (ASC 350). ASU 2017-04 removes Step 2 from the goodwill impairment test. The standard will become effective for the Company beginning in fiscal year 2021, with early adoption permitted. The Company early adopted this guidance beginning in the third quarter of fiscal year 2020 and the guidance did not have a material impact on the Company’s consolidated financial statements and disclosures.
Accounting Standards Update 2017-08 [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Description of new accounting pronouncements					In March 2017, the FASB issued ASU 2017-08, Receivables — Nonrefundable Fees and Other Costs (ASC 310-20): Premium Amortization on Purchased Callable Debt Securities. ASU 2017-08 amends the amortization period for certain callable debt securities held at a premium. The amendments require the premium to be amortized to the earliest call date. The Company adopted this guidance beginning in the first quarter of fiscal year 2020 and the guidance did not have a material impact on the Company’s consolidated financial statements and disclosures.
Accounting Standards Update 2017-12 [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Description of new accounting pronouncements					In August 2017, the FASB issued ASU 2017-12, Derivatives and Hedging (ASC 815): Targeted Improvements to Accounting for Hedging Activities. ASU 2017-12 improves the financial reporting of hedging relationships to better portray the economic results of an entity’s risk management activities in its financial statements and make certain targeted improvements to simplify the application of the hedge accounting guidance in current GAAP. The amendments in this update better align an entity’s risk management activities and financial reporting for hedging relationships through changes to both the designation and measurement guidance for qualifying hedging relationships and presentation of hedge results. In October 2018, the FASB issued ASU 2018-16, Derivatives and Hedging (ASC 815): Inclusion of the Secured Overnight Financing Rate (SOFR) Overnight Index SWAP (OIS) Rate as a Benchmark Interest Rate for Hedge Accounting Purposes, which permits use of the OIS rate based on SOFR as a U.S. benchmark interest rate for hedge accounting purposes and has the same effective date as ASU 2017-12. In April 2019, the FASB issued ASU 2019-04, Codification Improvements to ASC 815, Derivatives and Hedging, which clarifies certain aspects of ASC 815 and has the same effective date as ASU 2017-12. The Company adopted this guidance beginning in the first quarter of fiscal year 2020 and the guidance did not have a material impact on the Company’s consolidated financial statements and disclosures.
Accounting Standards Update 2018-09 [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Description of new accounting pronouncements					In July 2018, the FASB issued ASU 2018-09, Codification Improvements, which is related to a project by the FASB to facilitate codification updates for technical corrections, clarifications and other minor improvements. The new standard contains amendments that affect a wide variety of topics in the ASC. The effective date of the standard is dependent on the facts and circumstances of each amendment. Some amendments do not require transition guidance and were effective upon the issuance of this standard. A majority of the amendments in ASU 2018-09 became effective for the Company beginning in fiscal year 2020. The Company adopted the remainder of the amendments of this guidance in the first quarter of fiscal year 2020 and the guidance did not have a material impact on its 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 new standard will become effective for the Company beginning in fiscal year 2021, with early adoption permitted. The Company is currently evaluating the impact of this standard on its consolidated financial statements and disclosures.
Accounting Standards Update 2019-07 [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Description of new accounting pronouncements					In July 2019, the FASB issued ASU 2019-07, Codification Updates to SEC Sections. ASU 2019-07 modifies the disclosure and presentation requirements for a variety of codification topics by aligning them with the Securities and Exchange Commission’s (the SEC) regulations to eliminate redundancies and simplify the application of the codification. The Company adopted this guidance in the second quarter of fiscal year 2020 and the guidance did not have a material impact on the Company’s consolidated financial statements and disclosures.
Accounting Standards Update 2019-08 [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Description of new accounting pronouncements					In November 2019, the FASB issued ASU 2019-08, Compensation – Stock Compensation (ASC 718) and Revenue from Contracts with Customers (ASC 606): Codification Improvements – Share-Based Consideration Payable to a Customer. ASU 2019-08 expands the scope of ASC 718 to provide guidance for share-based payment awards granted to a customer in conjunction with selling goods or services accounted for under ASC 606. The Company early adopted this guidance beginning in the third quarter of fiscal year 2020 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, with early adoption permitted. 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, with early adoption permitted. The Company is currently evaluating the impact of this standard on its 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					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					88.00%	90.00%
U S Government as an Individual Customer [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Percentage of revenue					30.00%	26.00%
Commercial Customers [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Percentage of revenue					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
Purchase of treasury shares pursuant to vesting of certain RSU agreements | shares					385,604	427,088	335,295
Repurchase and immediate retirement of treasury shares pursuant to vesting of certain RSU agreements					$ 28,800,000	$ 28,800,000	$ 24,200,000
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					1,075,526	1,201,502	896,776
Indemnification Agreement [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Accrued reserves					$ 0	$ 0
Unfavorable Regulatory Action [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Accrued reserves					$ 7,800,000	4,900,000
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					$ 399,343,000	373,357,000
Accumulated depreciation and amortization					$ 165,700,000	142,600,000
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	978,118,000
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		$ 2,300,000				$ 185,700,000
Government Contracts Concentration Risk [Member] | Sales Revenue, Net [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Concentration risk, percentage					30.00%	26.00%	31.00%
Government Contracts Concentration Risk [Member] | Accounts Receivable [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Concentration risk, percentage					35.00%	32.00%
Customer Concentration Risk [Member] | Sales Revenue, Net [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Concentration risk, percentage					18.00%	20.00%	20.00%
Euro Retail Co [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Equity method investment ownership percentage			49.00%