Employee Benefit Plans Amounts Recognized in Balance Sheet (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Pension Plan | UNITED STATES
Defined Benefit Plans and Other Postretirement Benefit Plans
Current Pension Liability	$ 8.0	$ 7.7
Noncurrent Pension Liability	558.3	499.2
Noncurrent Pension Asset	0.0	0.0
Funded Status of Plan	566.3	506.9
Net Actuarial Gain (Loss) in Balance Sheet	(767.9)	(695.4)
Prior Service Credit in Balance Sheet	(0.6)	(0.7)
Pension Recognized in Balance Sheet, Gross of Deferred Tax	(768.5)	(696.1)
Pension Deferred Tax Asset in Balance Sheet	273.9	240.7
Pension Recognized in Balance Sheet, Net of Deferred Tax	(494.6)	(455.4)	$ (437.3)
Pension Plan | UNITED KINGDOM
Defined Benefit Plans and Other Postretirement Benefit Plans
Current Pension Liability	0.0	0.0
Noncurrent Pension Liability	5.9	4.1
Noncurrent Pension Asset	0.0	0.0
Funded Status of Plan	5.9	4.1
Net Actuarial Gain (Loss) in Balance Sheet	(70.5)	(63.1)
Prior Service Credit in Balance Sheet	(0.2)	(0.3)
Pension Recognized in Balance Sheet, Gross of Deferred Tax	(70.7)	(63.4)
Pension Deferred Tax Asset in Balance Sheet	16.0	14.5
Pension Recognized in Balance Sheet, Net of Deferred Tax	(54.7)	(48.9)	(37.3)
Other Postretirement Benefit Plans
Defined Benefit Plans and Other Postretirement Benefit Plans
Current Pension Liability	1.5	1.5
Noncurrent Pension Liability	109.7	115.8
Noncurrent Pension Asset	0.0	0.0
Funded Status of Plan	111.2	117.3
Net Actuarial Gain (Loss) in Balance Sheet	11.0	11.1
Prior Service Credit in Balance Sheet	2.9	3.1
Pension Recognized in Balance Sheet, Gross of Deferred Tax	13.9	14.2
Pension Deferred Tax Asset in Balance Sheet	5.4	5.3
Pension Recognized in Balance Sheet, Net of Deferred Tax	$ 19.3	$ 19.5	$ 27.4