Commitments and Contingencies - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Commitments And Contingencies [Line Items]
Rent expense	$ 17.5	$ 17.7	$ 17.9
Minimum
Commitments And Contingencies [Line Items]
LOC contract period requirement	1 year
Operating leases, term of contract	1 month
Maximum
Commitments And Contingencies [Line Items]
LOC contract period requirement	3 years
Operating leases, term of contract	5 years