Commitments and Contingencies - Components of Lease Cost and Other Information Related to Leases (Details) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2019 USD ($)	Sep. 30, 2019 USD ($)
Lease, Cost [Abstract]
Operating lease cost	$ 8.0	$ 24.7
Sublease income	(0.2)	(0.7)
Total lease cost	$ 7.8	$ 24.0
Weighted-average remaining lease term of operating leases	5 years	5 years
Weighted-average discount rate of operating leases	6.30%	6.30%