Retirement and Deferred Compensation Plans - Defined Contribution Plans and Deferred Compensation Plans (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Deferred compensation plans, asset and liability	$ 88.5	$ 98.0
Company Sponsored Plans
Defined Benefit Plan Disclosure [Line Items]
Total expense	17.7	17.6	$ 21.4
Statutory Plans
Defined Benefit Plan Disclosure [Line Items]
Total expense	$ 37.4	$ 35.6	$ 24.0