Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Pension Plan, Defined Benefit [Member]
Components of Net Periodic Benefit Cost
Service cost - benefits earned during the period	$ 1.9	$ 1.9	$ 3.8	$ 3.7
Interest cost on projected benefit obligation	6.7	7.6	13.4	15.2
Expected return on plan assets	(10.8)	(12.1)	(21.6)	(24.2)
Settlement loss	0.0	0.3	0.0	0.3
Amortization of prior service cost	0.3	0.2	0.5	0.4
Recognized actuarial net (gain) or loss	4.1	3.5	8.3	7.0
Net periodic benefit (income) cost	2.2	1.4	4.4	2.4
Other Postretirement Benefit Plan, Defined Benefit [Member]
Components of Net Periodic Benefit Cost
Service cost - benefits earned during the period	0.0	0.0	0.0	0.0
Interest cost on projected benefit obligation	0.0	0.1	0.0	0.1
Expected return on plan assets	0.0	0.0	0.0	0.0
Settlement loss	0.0	0.0	0.0	0.0
Amortization of prior service cost	(0.1)	(0.2)	(0.1)	(0.2)
Recognized actuarial net (gain) or loss	(0.3)	(0.2)	(0.6)	(0.4)
Net periodic benefit (income) cost	(0.4)	(0.3)	(0.7)	(0.5)
Bemis Investment Profit Sharing Plan and Other Defined Contribution Plans [Member]
Components of Net Periodic Benefit Cost
Defined contribution benefits plans	$ 8.0	$ 7.6	$ 15.1	$ 15.5