Summary of Significant Accounting Policies - Fair Value Measurements (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Aggregate maximum payout amount	$ 157.2
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration	84.2	$ 70.8
Change in the fair value of contingent consideration liabilities	13.4	$ (11.2)	$ (5.2)
Level 3 | Acquisition Without Maximum Earn-out
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration	$ 1.0
Level 3 | Volatility | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration liability, measurement input	0.204
Level 3 | Volatility | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration liability, measurement input	0.300
Level 3 | Discount Rate | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration liability, measurement input	0.016
Level 3 | Discount Rate | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration liability, measurement input	0.039