Revenue - Narrative (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2021	Dec. 31, 2020
Disaggregation Of Revenue [Line Items]
Payment terms for customers, lower range		30 days
Payment term for customers, upper range		120 days
Total		$ 137.3
Unearned revenue and customer deposits		83.2	$ 68.9
Other Current Liabilities [Member]
Disaggregation Of Revenue [Line Items]
Unearned revenue and customer deposits		2.2	1.6
Other Noncurrent Liabilities [Member]
Disaggregation Of Revenue [Line Items]
Contract liabilities, recognized, noncurrent		$ 57.2	$ 26.2
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		75.00%
Dedicated Fiber Agreement [Member] | Other Current Liabilities [Member]
Disaggregation Of Revenue [Line Items]
Unearned revenue and customer deposits		$ 0.5
Dedicated Fiber Agreement [Member] | Other Noncurrent Liabilities [Member]
Disaggregation Of Revenue [Line Items]
Contract liabilities, recognized, noncurrent		$ 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