Employee Benefit Plans Amounts Recognized in Other Comprehensive Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Pension Plan | UNITED STATES
Defined Benefit Plans and Other Postretirement Benefit Plans
Pension Recognized in Balance Sheet, Net of Deferred Tax, Beginning of Year	$ (455.4)	$ (437.3)
Amortization of Net Actuarial Loss (Gain)	18.7	20.2	$ 21.7
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, before Tax	(91.2)	(43.0)
Amortization of Prior Service Cost (Credit)	0.1	0.0	0.0
Change in Other Comprehensive Income, Curtailment Gain (Loss)	0.0	0.0
Change in Unrecognized Pension and Postretirement Benefit Costs, Tax Expense	33.2	4.7
Pension Recognized in Balance Sheet, Net of Deferred Tax, End of Year	(494.6)	(455.4)	(437.3)
Pension Plan | UNITED KINGDOM
Defined Benefit Plans and Other Postretirement Benefit Plans
Pension Recognized in Balance Sheet, Net of Deferred Tax, Beginning of Year	(48.9)	(37.3)
Amortization of Net Actuarial Loss (Gain)	1.1	0.9	0.6
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, before Tax	(8.5)	(15.1)
Amortization of Prior Service Cost (Credit)	0.0	0.0	0.0
Change in Other Comprehensive Income, Curtailment Gain (Loss)	0.1	0.0
Change in Unrecognized Pension and Postretirement Benefit Costs, Tax Expense	1.5	2.6
Pension Recognized in Balance Sheet, Net of Deferred Tax, End of Year	(54.7)	(48.9)	(37.3)
Other Postretirement Benefit Plans
Defined Benefit Plans and Other Postretirement Benefit Plans
Pension Recognized in Balance Sheet, Net of Deferred Tax, Beginning of Year	19.5	27.4
Amortization of Net Actuarial Loss (Gain)	0.0	(2.5)	0.0
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, before Tax	(0.1)	(7.3)
Amortization of Prior Service Cost (Credit)	(0.2)	(0.2)	(0.2)
Change in Other Comprehensive Income, Curtailment Gain (Loss)	0.0	0.0
Change in Unrecognized Pension and Postretirement Benefit Costs, Tax Expense	0.1	2.1
Pension Recognized in Balance Sheet, Net of Deferred Tax, End of Year	$ 19.3	$ 19.5	$ 27.4