Senior Notes and Other Long-Term Debt - Components of Long-Term Debt (Detail) - USD ($) $ in Thousands		Jun. 30, 2025	Mar. 31, 2025
Debt Instrument [Line Items]
Finance lease obligations (see Note 1)	[1]	$ 154,645	$ 158,473
Finance Lease, Liability, Statement of Financial Position [Extensible Enumeration]		Other long-term debt	Other long-term debt
Total debt		$ 6,741,529	$ 7,204,275
Unamortized discount, debt issuance costs and fair value adjustments made in purchase accounting		(156,753)	(168,166)
Less: current portion of long-term debt		52,161	503,825
Total long-term debt		6,532,615	6,532,284
2024 Inmarsat Term Loan Facility [Member]
Debt Instrument [Line Items]
Principal amount of debt		1,283,750	1,287,000
2031 Notes [Member]
Debt Instrument [Line Items]
Principal amount of debt		733,400	733,400
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 2029 Notes [Member]
Debt Instrument [Line Items]
Principal amount of debt		1,975,000	1,975,000
2025 Notes [Member]
Debt Instrument [Line Items]
Principal amount of debt	[1]		442,550
2022 Term Loan Facility [Member]
Debt Instrument [Line Items]
Principal amount of debt		679,000	680,750
2023 Term Loan Facility [Member]
Debt Instrument [Line Items]
Principal amount of debt		605,908	607,450
Immarsat 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		$ 9,826	$ 19,652

[1] On May 2, 2025, the 2025 Notes were redeemed in full.