Employee Benefits - Postretirement Plan and Summary Information for All Defined Benefit Plans (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Apr. 30, 2006	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Supplemental Executive Retirement Plans
Summary of benefit payments under the Company's various defined benefit plans, which reflect expected future employee service, as appropriate, expected to be paid in the future periods
2019		$ 1.1
2020		13.9
2021		1.1
2022		7.9
2023		1.0
2024-2028		4.4
Defined Benefit Plans
Summary of benefit payments under the Company's various defined benefit plans, which reflect expected future employee service, as appropriate, expected to be paid in the future periods
2019		4.3
2020		4.4
2021		4.7
2022		4.9
2023		5.2
2024-2028		$ 27.9
Supplemental Bonus Plan
Stock-Based Compensation
Number of shares of the entity to be contributed to the plan as a result of acquisition	258,006
Share liability to the plan to be settled in cash		65,955
Cash equivalent of share liability to the plan		$ 4.7
Expense (income) from mark to market adjustment		$ (0.8)	$ 0.6	$ 2.1