Senior Notes and Other Long-Term Debt - Components of Long-Term Debt (Detail) - USD ($) $ in Thousands	Mar. 31, 2025	Mar. 31, 2024
Debt Instrument [Line Items]
Finance lease obligations (see Note 1)	$ 158,473	$ 26,771
Finance Lease, Liability, Statement of Financial Position [Extensible Enumeration]	Other long-term debt	Other long-term debt
Total debt	$ 7,204,275	$ 7,475,842
Unamortized discount, debt issuance costs and fair value adjustments made in purchase accounting	(168,166)	(288,553)
Less: current portion of long-term debt	503,825	58,054
Total long-term debt	6,532,284	7,129,235
2024 Inmarsat Term Loan Facility [Member]
Debt Instrument [Line Items]
Principal amount of debt	1,287,000	1,300,000
2022 Term Loan Facility [Member]
Debt Instrument [Line Items]
Principal amount of debt	680,750	687,750
2023 Term Loan Facility [Member]
Debt Instrument [Line Items]
Principal amount of debt	607,450	613,617
Inmarsat Original Term Loan Facility [Member]
Debt Instrument [Line Items]
Principal amount of debt	300,000	300,000
Ex-Im Credit Facility [Member]
Debt Instrument [Line Items]
Principal amount of debt	19,652	39,304
2025 Notes [Member]
Debt Instrument [Line Items]
Principal amount of debt	442,550	700,000
Inmarsat 2026 Notes [Member]
Debt Instrument [Line Items]
Principal amount of debt		2,075,000
2027 Notes [Member]
Debt Instrument [Line Items]
Principal amount of debt	600,000	600,000
2028 Notes [Member]
Debt Instrument [Line Items]
Principal amount of debt	400,000	400,000
Inmarsat 2029 Notes [Member]
Debt Instrument [Line Items]
Principal amount of debt	1,975,000
2031 Notes [Member]
Debt Instrument [Line Items]
Principal amount of debt	$ 733,400	$ 733,400