Senior Notes and Other Long-Term Debt - Components of Long-Term Debt (Detail) - USD ($) $ in Thousands		Dec. 31, 2024	Mar. 31, 2024
Debt Instrument [Line Items]
Finance lease obligations (see Note 1)		$ 164,409	$ 26,771
Finance Lease, Liability, Statement of Financial Position [Extensible Enumeration]		Other long-term debt	Other long-term debt
Total debt		$ 7,218,294	$ 7,475,842
Unamortized discount, debt issuance costs and fair value adjustments made in purchase accounting		(175,569)	(288,553)
Less: current portion of long-term debt		506,922	58,054
Total long-term debt		6,535,803	7,129,235
2024 Inmarsat Term Loan Facility [Member]
Debt Instrument [Line Items]
Principal amount of debt		1,290,250	1,300,000
2022 Term Loan Facility [Member]
Debt Instrument [Line Items]
Principal amount of debt		682,500	687,750
2023 Term Loan Facility [Member]
Debt Instrument [Line Items]
Principal amount of debt		610,533	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	[1]		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

[1] On October 1, 2024, the Inmarsat 2026 Notes were repurchased and redeemed in full with the net proceeds of the Inmarsat 2029 Notes and cash on hand.