Benefit Plans and Other Postretirement Benefits, Benefit obligation and plan assets (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Jan. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Amounts recognized in the balance sheet as of December 31:
Accrued pension and postretirement benefit obligations		$ 272.0	$ 288.4
Accumulated other comprehensive loss, net		$ (201.0)	$ (469.0)
U.S.
Weighted average assumptions used to determine projected benefit obligations:
Rate of compensation increase (as a percent)		3.00%	3.00%
International Plans
Weighted average assumptions used to determine projected benefit obligations:
Rate of compensation increase (as a percent)		1.70%	1.63%
Pension Benefits
Change in projected benefit obligation:
Projected benefit obligation at beginning of year	$ 741.7	$ 703.3	$ 635.2
Service cost		9.6	9.0	$ 9.3
Interest cost		20.0	20.9	22.8
Acquisitions			47.4
Plan amendments			3.7
Actuarial (gain) loss		18.9	39.6
Foreign exchange translation		26.7	(17.3)
Benefits paid		(36.8)	(35.2)
Projected benefit obligation at end of year		741.7	703.3	635.2
Change in plan assets:
Fair value of plan assets at the beginning of the year	497.9	439.9	392.2
Actual return on plan assets		62.4	31.8
Employer contributions		22.5	22.2	20.9
Acquisitions			36.7
Foreign exchange translation		9.9	(7.8)
Benefits paid		(36.8)	(35.2)
Fair value of plan assets at end of year		497.9	439.9	392.2
Underfunded status at end of year		243.8	263.4
Amounts recognized in the balance sheet as of December 31:
Other accrued expenses		3.1	2.8
Accrued pension and postretirement benefit obligations		240.7	260.6
Accumulated other comprehensive loss, net		(164.4)	(191.8)
Accumulated benefit obligation
Accumulated benefit obligation		731.2	691.1
Pension Benefits | U.S.
Change in projected benefit obligation:
Projected benefit obligation at beginning of year	486.7	469.8	460.8
Service cost		6.7	6.2	6.5
Interest cost		15.3	15.4	17.4
Plan amendments			3.7
Actuarial (gain) loss		21.1	11.6
Benefits paid		(26.2)	(27.9)
Projected benefit obligation at end of year		486.7	469.8	460.8
Change in plan assets:
Fair value of plan assets at the beginning of the year	389.6	342.1	333.2
Actual return on plan assets		57.2	20.4
Employer contributions	80.0	16.5	16.4
Benefits paid		(26.2)	(27.9)
Fair value of plan assets at end of year		389.6	342.1	333.2
Underfunded status at end of year		97.1	127.7
Amounts recognized in the balance sheet as of December 31:
Accrued pension and postretirement benefit obligations		97.1	127.7
Accumulated other comprehensive loss, net		$ (110.5)	$ (129.3)
Weighted average assumptions used to determine projected benefit obligations:
Benefit obligation discount rate (as a percent)		3.48%	3.93%
Accumulated benefit obligation
Accumulated benefit obligation		$ 484.4	$ 465.8
Pension Benefits | International Plans
Change in projected benefit obligation:
Projected benefit obligation at beginning of year	255.0	233.5	174.4
Service cost		2.9	2.8	2.8
Interest cost		4.7	5.5	5.4
Acquisitions			47.4
Actuarial (gain) loss		(2.2)	28.0
Foreign exchange translation		26.7	(17.3)
Benefits paid		(10.6)	(7.3)
Projected benefit obligation at end of year		255.0	233.5	174.4
Change in plan assets:
Fair value of plan assets at the beginning of the year	108.3	97.8	59.0
Actual return on plan assets		5.2	11.4
Employer contributions		6.0	5.8
Acquisitions			36.7
Foreign exchange translation		9.9	(7.8)
Benefits paid		(10.6)	(7.3)
Fair value of plan assets at end of year		108.3	97.8	$ 59.0
Underfunded status at end of year		146.7	135.7
Amounts recognized in the balance sheet as of December 31:
Other accrued expenses		3.1	2.8
Accrued pension and postretirement benefit obligations		143.6	132.9
Accumulated other comprehensive loss, net		$ (53.9)	$ (62.5)
Weighted average assumptions used to determine projected benefit obligations:
Benefit obligation discount rate (as a percent)		2.21%	2.28%
Accumulated benefit obligation
Accumulated benefit obligation		$ 246.8	$ 225.3
Largest international pension plan | Pension Benefits | Unfunded Plan | International Plans
Change in projected benefit obligation:
Projected benefit obligation at beginning of year	$ 93.0	81.7
Projected benefit obligation at end of year		$ 93.0	$ 81.7