Commitments and Contingencies - Components of Lease Costs and Other Information Related to Leases (Details) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2019 USD ($)	Sep. 30, 2019 USD ($)
Commitments and Contingencies Disclosure [Abstract]
Operating lease cost	$ 12.2	$ 38.1
Variable lease cost	3.4	9.1
Total lease cost	15.6	47.2
Operating cash outflows from operating leases	12.7	36.4
ROU assets obtained in exchange for new operating lease liabilities	$ 3.9	$ 5.1
Weighted average remaining lease term (years)	6 years	6 years
Weighted average discount rate	4.40%	4.40%