Employee Benefit Plans Change in Projected Benefit Obligation Amount (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Pension Plan | UNITED STATES
Defined Benefit Plan, Change in Benefit Obligation
Benefit Obligation at Beginning of Year	$ 2,106.9	$ 1,933.3
Service Cost	11.0	10.9	$ 9.1
Interest Cost	73.0	83.3	79.8
Plan Participant Contributions	0.0	0.0
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	212.4	225.7
Benefits and Expenses Paid	(126.1)	(146.3)
Curtailment Gain	0.0	0.0
Change in Foreign Exchange Rates	0.0	0.0
Benefit Obligation at End of Year	2,277.2	2,106.9	1,933.3
Accumulated Benefit Obligation	2,277.2	2,106.9
Defined Benefit Plan, Change in Fair Value of Plan Assets
Fair Value of Plan Assets at Beginning of Year	1,600.0	1,454.9
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss)	227.9	282.7
Employer Contributions to Defined Benefit Plan	9.1	8.7
Plan Participant Contributions	0.0	0.0
Benefits and Expenses Paid	(126.1)	(146.3)
Effect of Foreign Exchange Rates on Plan Assets	0.0	0.0
Fair Value of Plan Assets at End of Year	1,710.9	1,600.0	1,454.9
Funded Status of Plan	566.3	506.9
Pension Plan | UNITED KINGDOM
Defined Benefit Plan, Change in Benefit Obligation
Benefit Obligation at Beginning of Year	256.9	211.0
Service Cost	0.0	0.0	0.0
Interest Cost	4.9	6.1	5.9
Plan Participant Contributions	0.0	0.0
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	33.8	34.9
Benefits and Expenses Paid	(5.1)	(4.8)
Curtailment Gain	(0.7)	0.0
Change in Foreign Exchange Rates	10.2	9.7
Benefit Obligation at End of Year	300.0	256.9	211.0
Accumulated Benefit Obligation	297.5	253.1
Defined Benefit Plan, Change in Fair Value of Plan Assets
Fair Value of Plan Assets at Beginning of Year	252.8	217.0
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss)	36.4	31.0
Employer Contributions to Defined Benefit Plan	0.0	0.0
Plan Participant Contributions	0.0	0.0
Benefits and Expenses Paid	(5.1)	(4.8)
Effect of Foreign Exchange Rates on Plan Assets	10.0	9.6
Fair Value of Plan Assets at End of Year	294.1	252.8	217.0
Funded Status of Plan	5.9	4.1
Other Postretirement Benefit Plans
Defined Benefit Plan, Change in Benefit Obligation
Benefit Obligation at Beginning of Year	127.2	125.9
Service Cost	0.0	0.0	0.0
Interest Cost	4.1	5.3	4.9
Plan Participant Contributions	0.1	0.2
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	(0.3)	7.0
Benefits and Expenses Paid	(10.6)	(11.2)
Curtailment Gain	0.0	0.0
Change in Foreign Exchange Rates	0.0	0.0
Benefit Obligation at End of Year	120.5	127.2	125.9
Defined Benefit Plan, Change in Fair Value of Plan Assets
Fair Value of Plan Assets at Beginning of Year	9.9	10.1
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss)	0.1	0.2
Employer Contributions to Defined Benefit Plan	9.8	10.6
Plan Participant Contributions	0.1	0.2
Benefits and Expenses Paid	(10.6)	(11.2)
Effect of Foreign Exchange Rates on Plan Assets	0.0	0.0
Fair Value of Plan Assets at End of Year	9.3	9.9	$ 10.1
Funded Status of Plan	$ 111.2	$ 117.3