Amount of decrease in right to consideration in exchange for good or service transferred to customer when right is conditioned on something other than passage of time from transfer to receivable due to right to consideration becoming unconditional.

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Revenue Recognition - Narrative (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2019	Dec. 31, 2018	Jan. 01, 2018
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Accumulated deficit	$ (2,255.2)	$ (2,225.7)
Accounting Standards Update 2014-09
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Revenue recognized from deferred revenue	12.1
Contract asset reclassified to receivables	$ 2.7
Cumulative Impact of Adopting Topic 606 \| Accounting Standards Update 2014-09
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Accumulated deficit			$ 12.9