Basis of Presentation - Additional Information (Detail)	3 Months Ended
	Jun. 30, 2018 USD ($) Segment shares	Jun. 30, 2017 USD ($) shares	Mar. 31, 2018 USD ($) shares
Company And Summary Of Significant Accounting Policies [Line Items]
Remaining performance obligations	$ 1,600,000,000
Number of reportable segments | Segment	3
Collections in excess of revenues and deferred revenues, recognized revenue	$ 50,600,000
Deferred customer contract amortization amount	4,400,000
Advertising costs	6,600,000	$ 1,200,000
Capitalized interest expense	6,200,000	14,600,000
Total capitalized costs related to patents	3,200,000		$ 3,200,000
Total capitalized costs related to orbital slots and other licenses	16,400,000		15,400,000
Accumulated amortization of patents, orbital slots and other licenses	2,600,000		2,500,000
Debt issuance costs capitalized	0	0
Capitalized costs, net, related to software developed for resale	246,788,000		246,792,000
Capitalized cost related to software development for resale	11,400,000	17,800,000
Amortization expense of capitalized software development costs	11,400,000	9,700,000
Self-insurance liability	4,600,000		$ 4,500,000
Repurchase and immediate retirement of treasury shares pursuant to vesting of certain RSU agreements	1,541,000
Stock-based compensation expense	19,126,000	15,507,000
Derivatives Designated as Hedging Instruments [Member] | Cash Flow Hedging [Member] | Foreign Currency Forward Contracts [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Notional value of foreign currency forward contracts outstanding	$ 6,500,000
Foreign currency forward contracts maturity, maximum	21 months
Gains or losses from ineffectiveness of derivative instruments	$ 0	$ 0
Common Stock Held in Treasury [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Shares of common stock held in treasury | shares	0		0
Purchase of treasury shares pursuant to vesting of certain RSU agreements | shares	94,200	27,514
Repurchase and immediate retirement of treasury shares pursuant to vesting of certain RSU agreements	$ 6,000,000	$ 1,900,000
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	270,785	72,811
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
Minimum [Member] | CPE Leased Equipment [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Property, equipment and satellites, estimated useful life (years)	4 years
Maximum [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Property, equipment and satellites, estimated useful life (years)	24 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
Maximum [Member] | CPE Leased Equipment [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Property, equipment and satellites, estimated useful life (years)	5 years
Prepaid Expenses and Other Current Assets [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Deferred customer contract costs	$ 17,600,000
Other Assets [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Deferred customer contract costs	32,200,000
Property and Equipment, Net [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Property and equipment	1,521,337,000		$ 1,442,398,000
Accumulated depreciation and amortization	749,130,000		719,910,000
Property and Equipment, Net [Member] | CPE Leased Equipment [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Property and equipment	310,506,000		298,746,000
Accumulated depreciation and amortization	130,100,000		129,000,000
Deferred Customer Contract Fulfillment Costs [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Deferred customer contract costs	5,600,000
Deferred Customer Contract Acquisition Costs [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Deferred customer contract costs	$ 44,200,000
Funded Research and Development from Customer Contracts [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Percentage of revenue	18.00%
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%
U.S. Government as an Individual Customer [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Percentage of revenue	28.00%
Commercial Customers [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Percentage of revenue	72.00%
Accounting Standards Update 2014-09 [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Revenue, practical expedient, financing component	true
Description of new accounting pronouncements	In May 2014, the Financial Accounting Standards Board (FASB) issued ASU 2014-09, Revenue from Contracts with Customers. ASU 2014-09 requires an entity to recognize the amount of revenue to which it expects to be entitled for the transfer of promised goods or services to a customer. This guidance replaced most existing revenue recognition guidance and became effective for the Company beginning in fiscal year 2019, including interim periods within that reporting period, based on the FASB decision in July 2015 (ASU 2015-14, Revenue from Contracts with Customers — Deferral of the Effective Date) to delay the effective date of the new revenue recognition standard by one year, but providing entities a choice to adopt the standard as of the original effective date. In March 2016, the FASB issued ASU 2016-08, Principal versus Agent Considerations (Reporting Revenue Gross versus Net), which clarifies the implementation guidance on principal versus agent considerations. In April 2016, the FASB issued ASU 2016-10, Identifying Performance Obligations and Licensing, which clarifies the implementation guidance on identifying performance obligations and the licensing implementation guidance. In May 2016, the FASB issued ASU 2016-12, Narrow-Scope Improvements and Practical Expedients, which provides practical expedient for contract modifications and clarification on assessing the collectability criterion, presentation of sales taxes, measurement date for non-cash consideration and completed contracts at transition. In December 2016, the FASB issued ASU 2016-20, Technical Corrections and Improvements to ASC 606, Revenue from Contracts with Customers, which provides for correction or improvement to the guidance previously issued in ASU 2014-09. These standards permit the use of either the retrospective or cumulative effect transition method. The Company adopted this standard effective as of April 1, 2018 utilizing the “modified retrospective method.” For additional information see Note 1 – Revenue recognition.
Accounting Standards Update 2016-01 [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Description of new accounting pronouncements	In January 2016, the FASB issued ASU 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities (ASC 825-10). ASU 2016-01 requires that most equity investments (except those accounted for under the equity method for accounting or those that result in consolidation of the investee) be measured at fair value, with subsequent changes in fair value recognized in net income (loss). The new guidance also impacts financial liabilities under the fair value option and the presentation and disclosure requirements for financial instruments. The new guidance was required to be applied by means of a cumulative-effect adjustment to the balance sheet as of the beginning of the fiscal year of adoption. ASU 2016-01 became effective for the Company in fiscal year 2019. The Company adopted this guidance beginning in the first quarter of fiscal year 2019 on a modified retrospective basis and the guidance did not have a material impact on the Company’s consolidated financial statements and disclosures.
Accounting Standards Update 2016-02 [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Description of new accounting pronouncements	In February 2016, the 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. The new guidance will become effective for the Company beginning in the first quarter of fiscal year 2020, with early adoption permitted. ASU 2016-02 will be adopted on a modified retrospective transition basis for leases existing at, or entered into after, the beginning of the earliest comparative period presented in the financial statements. The Company is currently evaluating the impact of this standard on its consolidated financial statements and disclosures.
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 (CECL) 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. 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 2016-15 [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Description of new accounting pronouncements	In August 2016, the FASB issued ASU 2016-15, Statement of Cash Flows (ASC 230). ASU 2016-15 makes eight targeted changes to how companies present and classify certain cash receipts and cash payments in the statement of cash flows. The new standard became effective for the Company beginning in fiscal year 2019, with early adoption permitted. The new standard required adoption on a retrospective basis unless impracticable to apply, in which case the Company would have been required to apply the amendments prospectively as of the earliest date practicable. The Company early adopted the guidance on a retrospective basis in the second quarter of fiscal year 2018 and as a result cash payments for debt prepayment and extinguishment were classified as cash outflows for financing activities in fiscal year 2018. Otherwise the adoption of this guidance did not have a material impact on the Company’s consolidated financial statements and disclosures.
Accounting Standards Update 2016-16 [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Description of new accounting pronouncements	In October 2016, the FASB issued ASU 2016-16, Income Taxes (ASC 740). ASU 2016-16 requires that an entity should recognize the income tax consequences of an intra-entity transfer of an asset other than inventory when the transfer occurs as opposed to when the asset has been sold to an outside party. The new standard became effective for the Company beginning in the first quarter of fiscal year 2019. The new standard requires adoption on a modified retrospective basis through a cumulative-effect adjustment directly to retained earnings as of the beginning of the period. The Company adopted this guidance beginning in the first quarter of fiscal year 2019 on a modified retrospective basis and the guidance did not have a material impact on the Company’s consolidated financial statements and disclosures.
Accounting Standards Update 2017-01 [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Description of new accounting pronouncements	In January 2017, the FASB issued ASU 2017-01, Business Combinations: Clarifying the Definition of a Business (ASC 805). ASU 2017-01 clarifies the definition of a business with the objective of adding guidance to assist entities with evaluating whether transactions should be accounted for as acquisitions (or disposals) of assets or businesses. The definition of a business affects many areas of accounting including acquisitions, disposals, goodwill, and consolidation. The new standard became effective for the Company beginning in the first quarter of fiscal year 2019. The Company adopted this guidance beginning in the first quarter of fiscal year 2019 on a prospective basis and the guidance did not have a material impact on the Company’s 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 is currently evaluating the impact of this standard on its consolidated financial statements and disclosures.
Accounting Standards Update 2017-05 [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Description of new accounting pronouncements	In February 2017, the FASB issued ASU 2017-05, Other Income — Gains and Losses from the Derecognition of Nonfinancial Assets (ASC 610-20): Clarifying the Scope of Asset Derecognition Guidance and Accounting for Partial Sales of Nonfinancial Assets. ASU 2017-05 clarifies the scope and accounting of a financial asset that meets the definition of an “in-substance nonfinancial asset” and defines the term “in-substance nonfinancial asset.” ASU 2017-05 also adds guidance for partial sales of nonfinancial assets. The standard became effective for the Company beginning in the first quarter of fiscal year 2019. The Company adopted this guidance beginning in the first quarter of fiscal year 2019 on a prospective basis 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 standard will become effective for the Company beginning in fiscal year 2020, with early adoption permitted. The Company is currently evaluating the impact of this standard on its consolidated financial statements and disclosures.
Accounting Standards Update 2017-09 [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Description of new accounting pronouncements	In May 2017, the FASB issued ASU 2017-09, Compensation — Stock Compensation (ASC 718): Scope of Modification Accounting. ASU 2017-09 provides guidance about which changes to the terms or conditions of a share-based payment award require an entity to apply modification accounting. The standard became effective for the Company beginning in the first quarter of fiscal year 2019. The Company early adopted this standard beginning in the fourth quarter of fiscal year 2018. 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. The standard will become effective for the Company beginning in fiscal year 2020, with early adoption permitted. The Company is currently evaluating the impact of this standard on its consolidated financial statements and disclosures.
Accounting Standards Update 2018-07 [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Description of new accounting pronouncements	In June 2018, the FASB issued ASU 2018-07, Compensation – Stock Compensation (ASC 718). ASU 2018-07 simplifies the accounting for nonemployee share-based payment transactions. Consequently, the accounting for share-based payments to nonemployees and employees will be substantially aligned. The new standard will become effective for the Company beginning in fiscal year 2020, with early adoption permitted. The Company early adopted the guidance in the first quarter of fiscal year 2019 and the guidance did not have a material impact on the Company’s consolidated financial statements and disclosures.
Unfavorable Regulatory Action [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Accrued reserves	$ 1,600,000		1,600,000
Indemnification Agreement [Member]
Company And Summary Of Significant Accounting Policies [Line Items]
Accrued reserves	$ 0		$ 0