Pension and Postretirement Benefits - Components of Net Periodic Benefit (Income) Expense (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 0.7		$ 0.8	$ 2.4	$ 2.2
Interest cost	38.2		54.1	116.2	161.7
Expected return on plan assets	(69.8)		(75.0)	(212.3)	(224.0)
Recognized net actuarial (gain) loss	45.8		44.8	138.6	133.8
Amortization of prior service benefit	(1.3)		(1.3)	(4.0)	(3.8)
Settlement losses	0.0		0.0	368.7	0.0
Net periodic pension expense/postretirement benefit (income) expense	13.6		23.4	409.6	69.9
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		40.6	88.2	121.8
Expected return on plan assets	(50.0)		(52.1)	(149.9)	(156.4)
Recognized net actuarial (gain) loss	34.0		33.8	101.8	101.6
Amortization of prior service benefit	(0.7)		(0.6)	(1.9)	(1.9)
Settlement losses	0.0	$ 158.0	0.0	158.0	0.0
Net periodic pension expense/postretirement benefit (income) expense	12.7		21.7	196.2	65.1
Pension Plans | International Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	0.7		0.8	2.4	2.2
Interest cost	8.8		13.5	28.0	39.9
Expected return on plan assets	(19.8)		(22.9)	(62.4)	(67.6)
Recognized net actuarial (gain) loss	11.8		11.0	36.8	32.2
Amortization of prior service benefit	(0.6)		(0.7)	(2.1)	(1.9)
Settlement losses	0.0		0.0	210.7	0.0
Net periodic pension expense/postretirement benefit (income) expense	0.9		1.7	213.4	4.8
Postretirement Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	0.1		0.1	0.3	0.3
Interest cost	0.5		1.1	1.3	3.3
Expected return on plan assets	(0.1)		(0.1)	(0.3)	(0.3)
Recognized net actuarial (gain) loss	(0.7)		0.3	(2.0)	0.8
Amortization of prior service benefit	(0.4)		(0.4)	(1.2)	(1.2)
Net periodic pension expense/postretirement benefit (income) expense	$ (0.6)		$ 1.0	$ (1.9)	$ 2.9