Commitments and Contingencies - Components of Lease Cost and Other Information Related to Leases (Details) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)
Lease, Cost [Abstract]
Operating lease cost	$ 8.2	$ 16.8
Sublease income	(0.3)	(0.5)
Total lease cost	$ 7.9	$ 16.3
Weighted-average remaining lease term of operating leases	5 years	5 years
Weighted-average discount rate of operating leases	6.30%	6.30%