Revenue (Summary of Contract Assets) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Revenue from Contract with Customer [Abstract]
Accounts receivable, less allowance for doubtful accounts	$ 188.5	$ 172.2
Deferred commissions	30.4	25.1
Total contract assets	$ 218.9	$ 197.3

Amount, after allowance for credit loss, of right to consideration from customer for product sold and service rendered in normal course of business, classified as current.

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