Fair Value Measurements - Additional Information (Detail) - USD ($)	6 Months Ended
Sep. 30, 2026	Mar. 31, 2026
Satellite Performance Incentives Obligation [Member] \| Satellites [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Expiration year of in-orbit satellite performance incentive obligation	2032
Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities measured at fair value on a recurring basis	$ 0	$ 0
Fair Value, Measurements, Recurring [Member] \| Level 2 [Member] \| Satellite Performance Incentives Obligation [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Satellite performance incentives obligation	8,000,000	6,100,000
Fair Value, Measurements, Recurring [Member] \| Level 2 [Member] \| 2027 Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of long term debt	597,800,000	597,800,000
Fair Value, Measurements, Recurring [Member] \| Level 2 [Member] \| 2028 Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of long term debt	397,700,000	395,000,000
Fair Value, Measurements, Recurring [Member] \| Level 2 [Member] \| 2031 Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of long term debt	719,200,000	724,900,000
Fair Value, Measurements, Recurring [Member] \| Level 2 [Member] \| Ex-Im Credit Facility [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of long term debt	170,100,000	186,200,000
Fair Value, Measurements, Recurring [Member] \| Level 2 [Member] \| Inmarsat Senior Secured Notes 2029 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of long term debt	$ 2,060,000,000.00	$ 2,070,000,000.00

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.

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