Benefit Plans and Other Postretirement Benefits, Net pension expense (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Jan. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
U.S.
Weighted average assumptions used to determine net periodic benefit cost/expense:
Rate of compensation increase (as a percent)		3.00%	3.00%	3.00%
International Plans
Weighted average assumptions used to determine net periodic benefit cost/expense:
Rate of compensation increase (as a percent)		1.63%	1.61%	1.45%
Pension Benefits
Defined Benefit Plan Disclosure
Plan contributions by employer		$ 22.5	$ 22.2	$ 20.9
Components of net pension expense:
Service cost		9.6	9.0	9.3
Interest cost		20.0	20.9	22.8
Expected return on plan assets		(30.7)	(30.1)	(29.1)
Amortization of prior service cost		2.7	2.4	2.3
Amortization of net actuarial losses		22.9	22.0	25.7
Net pension expense		24.5	24.2	31.0
Pension Benefits | U.S.
Defined Benefit Plan Disclosure
Plan contributions by employer	$ 80.0	16.5	16.4
Components of net pension expense:
Service cost		6.7	6.2	6.5
Interest cost		15.3	15.4	17.4
Expected return on plan assets		(27.2)	(26.2)	(25.9)
Amortization of prior service cost		2.7	2.4	2.3
Amortization of net actuarial losses		18.3	18.6	21.5
Net pension expense		$ 15.8	$ 16.4	$ 21.8
Weighted average assumptions used to determine net periodic benefit cost/expense:
Discount rate (as a percent)		3.93%	4.11%	3.75%
Expected long-term return on assets (as a percent)		7.75%	7.75%	8.00%
Pension Benefits | International Plans
Defined Benefit Plan Disclosure
Plan contributions by employer		$ 6.0	$ 5.8
Components of net pension expense:
Service cost		2.9	2.8	$ 2.8
Interest cost		4.7	5.5	5.4
Expected return on plan assets		(3.5)	(3.9)	(3.2)
Amortization of net actuarial losses		4.6	3.4	4.2
Net pension expense		$ 8.7	$ 7.8	$ 9.2
Weighted average assumptions used to determine net periodic benefit cost/expense:
Discount rate (as a percent)		2.28%	2.96%	2.91%
Expected long-term return on assets (as a percent)		3.80%	4.29%	5.47%