Fair Value Measurements - Narrative (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Percentage of decrease in future sales	10.00%
Decrease of estimated future sales in amount	$ 1.7
Contingent consideration	28.9	$ 41.4
Accrued Expenses
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration	2.1	11.8
Other Noncurrent Liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration	$ 26.9	$ 29.6