Revenue Recognition and Related Costs Revenue Recognition and Related Costs (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Disaggregation of Revenue [Line Items]
Trade receivables, allowance for doubtful accounts	$ 27.9		$ 27.9		$ 42.8
Contract assets	13.8		13.8		30.6
Deferred revenue	306.1		306.1		867.1
Revenue recognized			710.9
Aggregate assets associated with incremental costs to obtain a contract and contract fulfillment costs	47.4		47.4		92.6
Amortization related to contract costs	$ 29.4	$ 24.7	$ 99.0	$ 73.4
Performance obligation period			Revenue from customers who are subject to contracts is generally recognized over the term of such contracts, which is typically 12 months for our residential service contracts, one to three years for our mobile service contracts and one to five years
U.K. J.V. Entities
Disaggregation of Revenue [Line Items]
Deferred revenue					$ 463.7