Discontinued Operations - Components of Income (Details) $ in Millions		12 Months Ended
	Jun. 30, 2021 agreement Counterparty	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Discontinued Operations
Number of separate asset sales | agreement	2
Number of different buyers in asset sales | Counterparty	2
Other income (expense):
Income from discontinued operations		$ 839.1	$ 122.7
Atlantic and Astound broadband markets | Discontinued Operations, Disposed of by Sale
Discontinued operations - Components of income
Revenue		308.3
Costs and expenses
Operating (excluding depreciation and amortization)		112.0
Selling, general and administrative		11.8
Depreciation and amortization		41.0
Total costs and expenses		164.8
Income from operations		143.5
Other income (expense):
Interest income (expense)		0.4
Gain on sale of assets, net		1,001.8
Other income, net		0.1
Income from discontinued operations before provision for income tax		1,145.8
Income tax expense		(306.7)
Income from discontinued operations		$ 839.1
Atlantic and Astound broadband markets | Discontinued Operations, Held-for-sale
Discontinued operations - Components of income
Revenue			418.2
Costs and expenses
Operating (excluding depreciation and amortization)			165.0
Selling, general and administrative			12.3
Depreciation and amortization			79.6
Total costs and expenses			256.9
Income from operations			161.3
Other income (expense):
Interest income (expense)			(0.7)
Other income, net			0.5
Income from discontinued operations before provision for income tax			161.1
Income tax expense			(38.4)
Income from discontinued operations			$ 122.7