Employee Benefit Plans UK Pension Assets, Fair Value Measurement by Input Level (Details) - UNITED KINGDOM - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Plan Assets	$ 252.8	$ 217.0
Fair Value, Inputs, Level 1
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Plan Assets	89.8	84.0
Fair Value, Inputs, Level 2
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Plan Assets	0.0	0.0
Fair Value, Inputs, Level 3
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Plan Assets	0.0	0.0
Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Plan Assets	163.0	133.0
Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Plan Assets	252.8	217.0	$ 253.5
Diversified Growth Assets
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Plan Assets	163.0	133.0
Diversified Growth Assets | Fair Value, Inputs, Level 1
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Plan Assets	0.0	0.0
Diversified Growth Assets | Fair Value, Inputs, Level 2
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Plan Assets	0.0	0.0
Diversified Growth Assets | Fair Value, Inputs, Level 3
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Plan Assets	0.0	0.0
Diversified Growth Assets | Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Plan Assets	163.0	133.0
Fixed Interest and Index-linked Securities
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Plan Assets	89.6	81.3
Fixed Interest and Index-linked Securities | Fair Value, Inputs, Level 1
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Plan Assets	89.6	81.3
Fixed Interest and Index-linked Securities | Fair Value, Inputs, Level 2
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Plan Assets	0.0	0.0
Fixed Interest and Index-linked Securities | Fair Value, Inputs, Level 3
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Plan Assets	0.0	0.0
Fixed Interest and Index-linked Securities | Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Plan Assets	0.0	0.0
Cash Equivalents
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Plan Assets	0.2	2.7
Cash Equivalents | Fair Value, Inputs, Level 1
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Plan Assets	0.2	2.7
Cash Equivalents | Fair Value, Inputs, Level 2
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Plan Assets	0.0	0.0
Cash Equivalents | Fair Value, Inputs, Level 3
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Plan Assets	0.0	0.0
Cash Equivalents | Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Plan Assets	$ 0.0	$ 0.0