Retirement Plans (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Retirement Benefits [Abstract]
Matching contribution	25.00%
Maximum contributed compensation	4.00%
Additional matching contribution	12.50%
Expense related to retirement savings plan	$ 8.3	$ 10.1	$ 8.2