Revenue - Narrative (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2022	Dec. 31, 2021
Disaggregation Of Revenue [Line Items]
Payment terms for customers, lower range		30 days
Payment term for customers, upper range		120 days
Expected Revenue To Be Recognized		$ 180.0
Unearned revenue and customer deposits		81.6	$ 83.2
Other Current Liabilities [Member]
Disaggregation Of Revenue [Line Items]
Unearned revenue and customer deposits		3.2	2.2
Other Noncurrent Liabilities [Member]
Disaggregation Of Revenue [Line Items]
Contract liabilities, recognized, noncurrent		$ 74.2	57.2
Dedicated Fiber Agreement [Member]
Disaggregation Of Revenue [Line Items]
Indefeasible right of use of contract term	20 years	20 years
Revenue, Remaining Performance Obligation, Percentage		60.00%
Dedicated Fiber Agreement [Member] | Other Current Liabilities [Member]
Disaggregation Of Revenue [Line Items]
Unearned revenue and customer deposits		$ 1.4	0.5
Dedicated Fiber Agreement [Member] | Other Noncurrent Liabilities [Member]
Disaggregation Of Revenue [Line Items]
Contract liabilities, recognized, noncurrent		$ 51.5	$ 32.7
Minimum [Member]
Disaggregation Of Revenue [Line Items]
Customer contract term		1 year
SEA-US contract term		15 years
Indefeasible right of use of contract term		15 years
Maximum [Member]
Disaggregation Of Revenue [Line Items]
Customer contract term		5 years
SEA-US contract term		25 years
Indefeasible right of use of contract term		25 years
Indefeasible Right of Use, Maximum, in Years		30 years