Revenue Recognition and Related Costs (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
Revenue from Contract with Customer [Abstract]
Trade receivables, allowance for doubtful accounts	$ 45.8		$ 74.2
Contract assets	44.3	$ 26.1
Deferred revenue	877.9	999.5
Revenue recognized	901.4
Aggregate assets associated with incremental costs to obtain a contract and contract fulfillment costs	73.0	$ 68.1
Amortization related to contract costs	$ 99.8
Unsatisfied performance obligations, description of timing	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 for our B2B service contracts.