Contract Assets and Contract Liabilities (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Revenue from Contract with Customer [Abstract]
Contract assets - current	$ 30.3		$ 29.7
Contract assets - long-term	21.9		22.2
Deferred revenue - current	(292.2)		(294.4)
Deferred revenue - long-term	(158.1)		(157.2)
Deposit liabilities principally included in current deferred revenue	16.5		$ 21.2
Revenue recognized, previously included in deferred revenue	$ 104.9	$ 104.6

Amount, after allowance for credit loss, of right to consideration in exchange for good or service transferred to customer when right is conditioned on something other than passage of time, classified as current.

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-SubTopic 10
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- Definition

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Amount of obligation to transfer good or service to customer for which consideration has been received or is receivable, classified as current.

+ References

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Amount of obligation to transfer good or service to customer for which consideration has been received or is receivable, classified as noncurrent.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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Amount of revenue recognized that was previously included in balance of obligation to transfer good or service to customer for which consideration from customer has been received or is due.

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- Definition

The current portion, due within one year or one operating cycle, if longer, of deposits held other than customer deposits.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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