Pension plans (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Defined Benefit Plan Disclosure [Line Items]
Pension Expense	$ 68,700,000	$ 50,700,000	$ 53,000,000
Employer matching contribution on each pre-tax dollar for the first two percent of participant's contribution	0.50
Employee contribution for the first two percent of the plan	1.00
Employer's matching contribution on each pre-tax dollar for the next six percent of participant's contribution	0.25
Participant's contribution for the next six percent to the plan	1.00
Next percentage of participant contributions eligible for employer contribution match towards defined contribution plan	6.00%
Amount contributed to defined benefit multiemployear plans	1,300,000	1,500,000	1,300,000
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost - benefits earned during the period	14,700,000	13,500,000	12,900,000
Interest cost on benefit obligation	33,700,000	35,200,000	34,500,000
Expected return on plan assets	(43,500,000)	(40,300,000)	(39,900,000)
Settlement loss (gain)	12,700,000	(3,300,000)	0
Curtailment gain	0	(2,200,000)	0
Amortization of unrecognized transition obligation	200,000	200,000	200,000
Amortization of prior service cost	1,500,000	2,100,000	2,600,000
Recognized actuarial net (gain) or loss	28,500,000	23,400,000	16,200,000
Net periodic benefit (income) cost	47,800,000	28,600,000	26,500,000
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost - benefits earned during the period	300,000	300,000	300,000
Interest cost on benefit obligation	400,000	400,000	400,000
Amortization of prior service cost	(600,000)	(600,000)	(700,000)
Recognized actuarial net (gain) or loss	(300,000)	(400,000)	(500,000)
Net periodic benefit (income) cost	(200,000)	(300,000)	(500,000)
Defined Contribution Plans 401K Savings Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined contribution benefits plans	8,900,000	8,800,000	8,200,000
Bemis Investment Profit Sharing Plan and Other Defined Contribution Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined contribution benefits plans	$ 10,700,000	$ 11,800,000	$ 17,000,000