Pension and Postretirement Benefits - Components of Net Periodic Benefit (Income) Expense (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 0.5		$ 0.7	$ 1.7	$ 1.4
Interest cost	38.4		53.8	78.0	107.6
Expected return on plan assets	(68.4)		(73.9)	(142.5)	(149.0)
Recognized net actuarial (gain) loss	46.6		44.7	92.8	89.0
Amortization of prior service benefit	(1.4)		(1.3)	(2.7)	(2.5)
Settlement losses	210.7		0.0	368.7	0.0
Net periodic pension expense/postretirement benefit (income) expense	226.4		24.0	396.0	46.5
Pension Plans | U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	0.0		0.0	0.0	0.0
Interest cost	29.4		40.8	58.8	81.2
Expected return on plan assets	(48.5)		(52.0)	(99.9)	(104.3)
Recognized net actuarial (gain) loss	34.6		34.3	67.8	67.8
Amortization of prior service benefit	(0.6)		(0.7)	(1.2)	(1.3)
Settlement losses	0.0	$ 158.0	0.0	158.0	0.0
Net periodic pension expense/postretirement benefit (income) expense	14.9		22.4	183.5	43.4
Pension Plans | International Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	0.5		0.7	1.7	1.4
Interest cost	9.0		13.0	19.2	26.4
Expected return on plan assets	(19.9)		(21.9)	(42.6)	(44.7)
Recognized net actuarial (gain) loss	12.0		10.4	25.0	21.2
Amortization of prior service benefit	(0.8)		(0.6)	(1.5)	(1.2)
Settlement losses	210.7		0.0	210.7	0.0
Net periodic pension expense/postretirement benefit (income) expense	211.5		1.6	212.5	3.1
Postretirement Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	0.1		0.1	0.2	0.2
Interest cost	0.4		1.1	0.8	2.2
Expected return on plan assets	(0.1)		(0.1)	(0.2)	(0.2)
Recognized net actuarial (gain) loss	(0.7)		0.2	(1.3)	0.5
Amortization of prior service benefit	(0.4)		(0.4)	(0.8)	(0.8)
Net periodic pension expense/postretirement benefit (income) expense	$ (0.7)		$ 0.9	$ (1.3)	$ 1.9