Employee Benefit Plans, 401(k) Plan and Other Retirement Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Other Retirement Benefits [Abstract]
Supplemental retirement benefits for retired executives under other retirement benefits plan	$ 2.0	$ 2.4
Expense related to other retirement benefits plan	0.1	0.1	$ 0.2
401(K) Plan [Member]
Defined benefit plan disclosure [Abstract]
Employer contribution to plan	$ 3.2	$ 2.8	$ 2.7