Revenue Recognition and Related Costs (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Revenue from Contract with Customer [Abstract]
Trade receivables, allowance for doubtful accounts	$ 44.2		$ 42.8
Contract assets	23.6		30.6
Deferred revenue	790.2		867.1
Revenue recognized	555.6
Aggregate assets associated with incremental costs to obtain a contract and contract fulfillment costs	90.5		$ 92.6
Amortization related to contract costs	$ 37.7	$ 24.4
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