Acquisitions - Additional Information (Detail) shares in Thousands, € in Millions			1 Months Ended	3 Months Ended		6 Months Ended
	Nov. 08, 2021 USD ($) shares	Apr. 30, 2021 USD ($) shares	Mar. 31, 2017 USD ($)	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)	Apr. 30, 2021 EUR (€)
Business Acquisition [Line Items]
Net cash outlay after acquiree's cash on hand							$ 138,668,000
Shares issued in connection with acquisition of business							207,169,000
Total revenues				$ 656,683,000	$ 609,157,000	$ 1,228,117,000	1,179,937,000
Euro Broadband Infrastructure Sarl [Member]
Business Acquisition [Line Items]
Equity method investment ownership percentage			49.00%
Euro Broadband Infrastructure Sarl Step Acquisition [Member]
Business Acquisition [Line Items]
Percentage of additional interest in subsidiary acquired		51.00%						51.00%
Ownership percentage after completing the acquisition		100.00%						100.00%
The consideration transferred		$ 327,400,000	$ 160,400,000
Payments to acquire business		167,000,000.0
Euro Infrastructure Co.’s cash on hand		121,700,000
Net cash outlay after acquiree's cash on hand		$ 51,000,000.0
Contingent consideration arrangements		the Company may pay or receive up to €20.0 million, or approximately $19.3 million, in cash.				up to plus or minus €20.0 million
Euro Broadband Infrastructure Sarl Step Acquisition [Member] | Maximum [Member]
Business Acquisition [Line Items]
Amount of estimated purchase price consideration to be settled among the parties over the next 24 months from the closing date		$ 19,300,000						€ 20.0
RigNet, Inc [Member]
Business Acquisition [Line Items]
The consideration transferred		317,900,000
Shares issued in connection with acquisition of business		$ 207,200,000
Shares issued in connection with acquisition of business, net of issuance costs, shares | shares		4,000
Pay down of outstanding borrowings of acquiree		$ 107,300,000
Remaining amount payable				0		$ 0
Total revenues					45,200,000		79,200,000
Net losses					(9,900,000)		(16,200,000)
RigNet, Inc [Member] | Selling General and Administrative Expenses [Member]
Business Acquisition [Line Items]
Merger-related transaction costs				$ 0	$ 7,100,000	$ 0	$ 7,100,000
RigNet, Inc [Member] | Maximum [Member]
Business Acquisition [Line Items]
Contingent consideration liability		$ 13,800,000
Inmarsat [Member]
Business Acquisition [Line Items]
Consideration payable under the Share Purchase Agreement in cash, subject to adjustments	$ 850,000,000.0
Reduction Of Cash Purchase Price Consideration To Be Paid Upon Completion Of Acquisition	$ 299,300,000
Consideration payable under the Share Purchase Agreement in common stock, subject to adjustments | shares	46,360
Termination fee payable upon termination of the Share Purchase Agreement under certain circumstances	$ 200,000,000.0
Reimbursement of certain out-of-pocket expenses of certain sellers upon termination of the Share Purchase Agreement under certain circumstances	40,000,000.0
Financing commitments in connection with acquisition	1,600,000,000
Inmarsat Legal Entity [Member]
Business Acquisition [Line Items]
Distributed earnings	299,300,000
Principal amount of senior secured debt	2,100,000,000
Outstanding indebtedness borrowings under the Credit Facility	$ 2,400,000,000