Segment Information - Analysis of Operations by Reportable Segment (Details) - USD ($) $ in Millions		3 Months Ended																12 Months Ended
		Dec. 31, 2017		Sep. 30, 2017	[2]	Jun. 30, 2017	[3]	Mar. 31, 2017	[4]	Dec. 31, 2016		Sep. 30, 2016	[6]	Jun. 30, 2016	[7]	Mar. 31, 2016	[8]	Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 2015
Segment Reporting Information [Line Items]
Net sales		$ 1,684.3	[1]	$ 1,640.1		$ 1,584.0		$ 1,536.5		$ 1,476.6	[5]	$ 1,484.0		$ 1,417.4		$ 1,401.0		$ 6,444.9		$ 5,779.0		$ 5,741.7
Operating Income (Loss)		252.0	[1]	$ 242.3		$ 233.8		$ 203.1		192.9	[5]	$ 206.4		$ 200.2		$ 180.8		931.2		780.3		750.0
Interest expense, net																		(102.6)	[9]	(91.8)		(85.5)
Segment income (loss) from operations																		828.6		688.5		664.5
Depreciation, Amortization, and Depletion																		391.4		358.0		356.5
Capital Expenditures	[10]																	343.0		274.3		314.5
Assets		6,197.5								5,777.0								6,197.5		5,777.0		5,272.3
Intersegment Eliminations
Segment Reporting Information [Line Items]
Net sales																		(148.4)		(146.6)		(137.0)
Segment Reconciling Items
Segment Reporting Information [Line Items]
Net sales																		(148.4)		(146.6)		(137.0)
Packaging
Segment Reporting Information [Line Items]
Net sales																		5,288.6		4,577.4		4,474.1
Operating Income (Loss)																		943.7	[11]	711.0	[12]	714.9	[13]
Depreciation, Amortization, and Depletion																		317.5		293.3		297.3
Capital Expenditures	[10]																	305.1		239.9		250.3
Assets		4,933.6								4,530.5								4,933.6		4,530.5		4,027.9
Packaging | Intersegment Eliminations
Segment Reporting Information [Line Items]
Net sales																		23.7		7.4		3.2
Packaging | Operating Segments
Segment Reporting Information [Line Items]
Net sales																		5,312.3		4,584.8		4,477.3
Paper
Segment Reporting Information [Line Items]
Net sales																		1,051.8		1,093.9		1,143.1
Operating Income (Loss)																		61.5	[14]	138.1	[15]	112.5	[16]
Depreciation, Amortization, and Depletion																		67.6		59.6		54.9
Capital Expenditures	[10]																	22.6		31.6		58.5
Assets		945.2								946.2								945.2		946.2		976.5
Paper | Operating Segments
Segment Reporting Information [Line Items]
Net sales																		1,051.8		1,093.9		1,143.1
Corporate and Other
Segment Reporting Information [Line Items]
Net sales																		104.5		107.7		124.5
Operating Income (Loss)																		(74.0)	[17]	(68.9)	[18]	(77.4)	[19]
Depreciation, Amortization, and Depletion																		6.3		5.1		4.3
Capital Expenditures	[10]																	15.3		2.8		5.7
Assets		$ 318.7								$ 300.3								318.7		300.3		267.9
Corporate and Other | Intersegment Eliminations
Segment Reporting Information [Line Items]
Net sales																		124.7		139.2		133.8
Corporate and Other | Operating Segments
Segment Reporting Information [Line Items]
Net sales																		$ 229.2		$ 246.9		$ 258.3

[1] Includes $7.6 million of income primarily related to the sale of land corresponding to the closure of a corrugated products facility, partially offset by closure costs related to corrugated products facilities, a paper administration facility, and a corporate administration facility ($4.7 million after-tax or $0.05 per diluted share) and $0.9 million of charges related to the Sacramento Container acquisition and integration costs related to other recent acquisitions ($0.5 million after-tax or $0.01 per diluted share), and $8.0 million of charges related to our determination to discontinue production of uncoated free sheet and coated one-side grades at the Wallula, Washington mill in the second quarter of 2018 and convert the No. 3 paper machine to a high-performance 100% virgin kraft linerboard machine ($4.6 million after-tax or $0.05 per diluted share). Also includes $1.8 million of expense related to the write-off of deferred debt issuance costs in connection with the December 2017 debt refinancing ($1.1 million after-tax or $0.01 per diluted share), $2.0 million gain related to the expiration of a repurchase option corresponding to timberland previously sold ($1.2 million after-tax or 0.01 per diluted share), and $122.1 million of estimated income tax benefit related to the enactment in December 2017 of the Tax Cuts and Jobs Act (H.R.1) primarily for the re-measurement of our net deferred tax liability as a result of the reduction in the U.S. corporate income tax rate ($1.29 per diluted share).

[2] Includes $0.9 million of charges related to the closure of corrugated products facilities, a paper administration facility, and a lump sum settlement of a multiemployer pension plan withdrawal liability for one of our corrugated products facilities ($0.6 million after-tax or $0.01 per diluted share) and $0.5 million of charges related to the Sacramento Container acquisition and integration costs related to other recent acquisitions ($0.3 million after-tax or $0.0 per diluted share). Also includes $25.3 million of charges related to our determination to discontinue production of uncoated free sheet and coated one-side grades at the Wallula, Washington mill in the second quarter of 2018 and convert the No. 3 paper machine to a high-performance 100% virgin kraft linerboard machine ($15.5 million after-tax or $0.16 per diluted share) and $3.3 million of tax expense for the change in value of deferred taxes as a result of an internal legal entity consolidation that will simplify future operating activities ($0.04 per diluted share).

[3] Includes $0.3 million of charges related to the closure of corrugated products facilities ($0.3 million after-tax or $0.0 per diluted share) and $0.2 million of charges related to TimBar Corporation and Columbus Container integration costs ($0.1 after-tax or $0.0 per diluted share).

[4] Includes $0.6 million of charges related to the closure of corrugated products facilities and lump sum settlement of a multiemployer pension plan withdrawal liability for one of corrugated products facilities ($0.4 million after-tax or $0.1 per diluted share) and $0.2 million of charges related to TimBar Corporation and Columbus Container integration costs ($0.1 million after-tax or $0.0 per diluted share). Also includes $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 ($3.1 million after-tax or $0.03 per diluted share) and $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 ($1.4 million after-tax or $0.01 per diluted share).

[5] Includes $4.5 million of charges related to the closure of a corrugated products facility and a paper products facility ($2.9 million after-tax or $0.03 per diluted share), $2.7 million of costs related to ceased production of softwood market pulp operations at our Wallula, Washington mill and the permanent shutdown of the No. 1 machine ($1.8 million after-tax or $0.02 per diluted share), and $1.2 million of charges related to the TimBar Corporation and Columbus Container acquisitions and integration ($0.8 million after-tax or $0.01 per diluted share).

[6] Includes $2.0 million of charges related to the closure of a corrugated products facility and a paper products facility ($1.4 million after-tax or $0.02 per diluted share) and $2.9 million of charges related to the TimBar Corporation and Columbus Container acquisitions and integration ($1.9 million after-tax or $0.02 per diluted share).

[7] Includes $2.6 million of charges related to the closure of corrugated products facilities, a paper products facility, and a lump sum settlement of a multiemployer pension plan withdrawal liability for one of our corrugated products facilities ($1.6 million after-tax or $0.02 per diluted share) and $0.3 million of charges related to the TimBar Corporation acquisition and integration ($0.2 million after-tax or $0.0 per diluted share).

[8] Includes $2.8 million of charges related to the closure of a corrugated products facility and a paper products facility ($1.9 million after-tax or $0.02 per diluted share).

[9] Includes $1.8 million of expense related to the write-off of deferred debt issuance costs in connection with the December 2017 debt refinancing.

[10] Includes “Additions to property, plant, and equipment” and excludes cash used for “Acquisitions of businesses, net of cash acquired” as reported on our Consolidated Statements of Cash Flows.

[11] (a)Includes the following: $7.2 million of income, net, primarily related to the sale of land corresponding to the closure of a corrugated products facility, partially offset by closure costs related to corrugated products facilities, and a lump sum settlement of a multiemployer pension plan withdrawal liability for one of our corrugated products facilities. $1.7 million of charges related to the Sacramento Container acquisition and integration costs related to other recent acquisitions. $2.0 million gain related to the expiration of a repurchase option corresponding to timberland previously sold. $1.6 million of income related to a working capital adjustment from the April 2015 sale of our Hexacomb corrugated manufacturing operations in Europe and Mexico. $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.

[12] Includes $10.2 million of closure costs related to corrugated product facilities and a lump sum settlement of a multiemployer pension plan withdrawal liability for one of our corrugated products facilities and $4.2 million of acquisition-related costs for the TimBar Corporation and Columbus Container acquisitions.

[13] Includes net charges of $2.0 million primarily related to restructuring activities at our mill in DeRidder, Louisiana and $4.1 million of Boise acquisition integration-related and other costs.

[14] Includes $33.4 million of charges related to our determination to discontinue production of uncoated free sheet and coated one-side grades at the Wallula, Washington mill in the second quarter of 2018 and convert the No. 3 paper machine to a high-performance 100% virgin kraft linerboard machine and $0.4 million of charges related to the closure costs of a paper administration facility.

[15] Includes $2.7 million of costs related to ceased softwood market pulp operations at our Wallula, Washington mill and the permanent shut down of the No.1 machine and $1.7 million of closure costs related to a paper products facility.

[16] In September 2015, we sold the remaining land, buildings, and equipment at our paper mill site in St. Helens, Oregon where we ceased paper production in December 2012. We recorded a $6.7 million gain on the sale.

[17] Includes $1.0 million of charges related to the closure costs of a corporate administration facility and $0.7 million of income related to a working capital adjustment from the April 2015 sale of our Hexacomb corrugated manufacturing operations in Europe and Mexico.

[18] Includes $0.3 million of acquisition-related costs related to the TimBar Corporation acquisition.

[19] Includes $9.3 million of Boise acquisition integration-related and other costs. These costs primarily relate to professional fees, severance, retention, relocation, travel, and other integration-related costs.