Employee Benefit Plans Change in Projected Benefit Obligation Amount (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
UNITED STATES
Defined Benefit Plan, Change in Fair Value of Plan Assets
Fair Value of Plan Assets at Beginning of Year	$ 1,456.8
Fair Value of Plan Assets at End of Year	1,596.8	$ 1,456.8
UNITED KINGDOM
Defined Benefit Plan, Change in Fair Value of Plan Assets
Fair Value of Plan Assets at Beginning of Year	217.0
Fair Value of Plan Assets at End of Year	252.8	217.0
Pension Plan | UNITED STATES
Defined Benefit Plan, Change in Benefit Obligation
Benefit Obligation at Beginning of Year	1,933.3	2,136.9
Service Cost	10.9	9.1	$ 7.9
Interest Cost	83.3	79.8	84.5
Plan Participant Contributions	0.0	0.0
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	225.7	(210.3)
Benefits and Expenses Paid	(146.3)	(82.2)
Plan Amendments	0.0	0.0	7.6
Change in Foreign Exchange Rates	0.0	0.0
Benefit Obligation at End of Year	2,106.9	1,933.3	2,136.9
Accumulated Benefit Obligation	2,106.9	1,933.3
Defined Benefit Plan, Change in Fair Value of Plan Assets
Fair Value of Plan Assets at Beginning of Year	1,454.9	1,582.6
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss)	282.7	(53.6)
Employer Contributions to Defined Benefit Plan	8.7	8.1
Plan Participant Contributions	0.0	0.0
Benefits and Expenses Paid	(146.3)	(82.2)
Effect of Foreign Exchange Rates on Plan Assets	0.0	0.0
Fair Value of Plan Assets at End of Year	1,600.0	1,454.9	1,582.6
Funded Status of Plan	506.9	478.4
Pension Plan | UNITED KINGDOM
Defined Benefit Plan, Change in Benefit Obligation
Benefit Obligation at Beginning of Year	211.0	243.8
Service Cost	0.0	0.0	0.0
Interest Cost	6.1	5.9	6.2
Plan Participant Contributions	0.0	0.0
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	34.9	(18.9)
Benefits and Expenses Paid	(4.8)	(7.3)
Plan Amendments	0.0	(0.3)
Change in Foreign Exchange Rates	9.7	(12.8)
Benefit Obligation at End of Year	256.9	211.0	243.8
Accumulated Benefit Obligation	253.1	205.0
Defined Benefit Plan, Change in Fair Value of Plan Assets
Fair Value of Plan Assets at Beginning of Year	217.0	253.5
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss)	31.0	(16.0)
Employer Contributions to Defined Benefit Plan	0.0	0.0
Plan Participant Contributions	0.0	0.0
Benefits and Expenses Paid	(4.8)	(7.3)
Effect of Foreign Exchange Rates on Plan Assets	9.6	(13.2)
Fair Value of Plan Assets at End of Year	252.8	217.0	253.5
Funded Status of Plan	4.1	(6.0)
Other Postretirement Benefit Plans
Defined Benefit Plan, Change in Benefit Obligation
Benefit Obligation at Beginning of Year	125.9	139.5
Service Cost	0.0	0.0	0.0
Interest Cost	5.3	4.9	5.9
Plan Participant Contributions	0.2	0.2
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	7.0	(7.6)
Benefits and Expenses Paid	(11.2)	(11.1)
Plan Amendments	0.0	0.0
Change in Foreign Exchange Rates	0.0	0.0
Benefit Obligation at End of Year	127.2	125.9	139.5
Defined Benefit Plan, Change in Fair Value of Plan Assets
Fair Value of Plan Assets at Beginning of Year	10.1	10.5
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss)	0.2	0.1
Employer Contributions to Defined Benefit Plan	10.6	10.4
Plan Participant Contributions	0.2	0.2
Benefits and Expenses Paid	(11.2)	(11.1)
Effect of Foreign Exchange Rates on Plan Assets	0.0	0.0
Fair Value of Plan Assets at End of Year	9.9	10.1	$ 10.5
Funded Status of Plan	$ 117.3	$ 115.8