Senior Notes and Other Long-Term Debt - Components of Long-Term Debt (Detail) - USD ($) $ in Thousands		Sep. 30, 2024	Mar. 31, 2024
Debt Instrument [Line Items]
Finance lease obligations (see Note 1)		$ 20,822	$ 26,771
Finance Lease, Liability, Statement of Financial Position [Extensible Enumeration]		Other long-term debt	Other long-term debt
Total debt		$ 9,064,558	$ 7,475,842
Unamortized discount, debt issuance costs and fair value adjustments made in purchase accounting		(281,649)	(288,553)
Less: current portion of long-term debt	[1]	2,377,989	58,054
Total long-term debt		6,404,920	7,129,235
2031 Notes [Member]
Debt Instrument [Line Items]
Principal amount of debt		733,400	733,400
Inmarsat 2029 Notes [Member]
Debt Instrument [Line Items]
Principal amount of debt		1,975,000
2028 Notes [Member]
Debt Instrument [Line Items]
Principal amount of debt		400,000	400,000
2027 Notes [Member]
Debt Instrument [Line Items]
Principal amount of debt		600,000	600,000
Inmarsat 2026 Notes [Member]
Debt Instrument [Line Items]
Principal amount of debt	[2]	1,973,275	2,075,000
2025 Notes [Member]
Debt Instrument [Line Items]
Principal amount of debt		442,550	700,000
2022 Term Loan Facility [Member]
Debt Instrument [Line Items]
Principal amount of debt		686,000	687,750
2023 Term Loan Facility [Member]
Debt Instrument [Line Items]
Principal amount of debt		610,533	613,617
Inmarsat Term Loan Facility [Member]
Debt Instrument [Line Items]
Principal amount of debt		1,593,500	1,600,000
Ex-Im Credit Facility [Member]
Debt Instrument [Line Items]
Principal amount of debt		$ 29,478	$ 39,304

[1] As of September 30, 2024, current portion of long-term debt included the 2025 Notes and the Inmarsat 2026 Notes.

[2] The Inmarsat 2026 Notes were redeemed in full with the net proceeds of the Inmarsat 2029 Notes on October 1, 2024, together with cash on hand, subsequent to quarter end.