Segment Information (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2018		Mar. 31, 2017
Segment Reporting Information [Line Items]
Net sales		$ 1,690.6		$ 1,536.5
Operating Income (Loss)	[1]	212.9		203.4
Interest expense, net and other	[1]	(26.3)		(24.3)
Income before taxes	[1]	186.6		179.1
Intersegment Eliminations
Segment Reporting Information [Line Items]
Net sales		(35.3)		(33.9)
Segment Reconciling Items
Segment Reporting Information [Line Items]
Net sales		(35.3)		(33.9)
Packaging
Segment Reporting Information [Line Items]
Net sales		1,396.6		1,251.3
Operating Income (Loss)	[1]	224.7	[2]	192.5	[3]
Packaging | Intersegment Eliminations
Segment Reporting Information [Line Items]
Net sales		6.3		5.7
Packaging | Operating Segments
Segment Reporting Information [Line Items]
Net sales		1,402.9		1,257.0
Paper
Segment Reporting Information [Line Items]
Net sales		269.4		259.2
Operating Income (Loss)	[1]	7.2	[2]	27.9
Paper | Operating Segments
Segment Reporting Information [Line Items]
Net sales		269.4		259.2
Corporate and Other
Segment Reporting Information [Line Items]
Net sales		24.6		26.0
Operating Income (Loss)	[1]	(19.0)	[2]	(17.0)	[3]
Corporate and Other | Intersegment Eliminations
Segment Reporting Information [Line Items]
Net sales		29.0		28.2
Corporate and Other | Operating Segments
Segment Reporting Information [Line Items]
Net sales		$ 53.6		$ 54.2

[1] (a)Effective January 1, 2018, the Company adopted ASU 2017-07, Compensation: Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost and applied this standard retrospectively to the prior period reflected herein. This new standard requires the presentation of non-service cost components of net periodic benefits expense to be shown separately outside the subtotal of operating income in the income statement. See Note 2, New and Recently Adopted Accounting Standards, for more information. The components of our financial statements affected by the change in presentation of operating and non-operating pension expense as originally reported in 2017 and as adjusted for the requirements per the new standard are as follows (dollars in millions): Segment income (loss) March 31, 2017 As Reported Non-Operating Pension Adjustment March 31, 2017 Adjusted Packaging $190.8 $1.7 $192.5 Paper 29.8 (1.9) 27.9 Corporate (17.5) 0.5 (17.0) Income from operations 203.1 0.3 203.4 Interest expense, net and other (24.0) (0.3) (24.3) Income before taxes $179.1 $— $179.1

[2] Includes $0.3 million of charges consisting of closure costs related to corrugated products facilities and a corporate administration facility and $8.8 million of charges related to the announced second quarter 2018 discontinuation of uncoated free sheet and coated one-side grades at the Wallula, Washington mill associated with the conversion of the No. 3 paper machine to a high-performance 100% virgin kraft linerboard machine.

[3] (c)Includes the following: 1.$0.8 million of charges consisting of closure costs related to corrugated products facilities, integration costs related to the TimBar Corporation and Columbus Container Inc. acquisitions, and costs related to a lump sum settlement payment of a multiemployer pension plan withdrawal liability for one of our corrugated products facilities. 2.$5.0 million of costs for the property damage and business interruption insurance deductible corresponding to the February 2017 explosion at our DeRidder, Louisiana mill. 3.$2.3 million of income related to a working capital adjustment from the April 2015 sale of our Hexacomb corrugated manufacturing operations in Europe and Mexico.