Lease Commitments - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Schedule of Leased Assets [Line Items]
Rent expense	$ 36.7	$ 42.3	$ 40.4
Minimum
Schedule of Leased Assets [Line Items]
Lease term	5 years
Maximum
Schedule of Leased Assets [Line Items]
Lease term	20 years