Segment Information - Segment Sales to External Customers by Product Line (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenue from External Customer [Line Items]
Segment sales to external customers	$ 1,390.9	$ 1,470.8	$ 1,454.3	$ 1,425.7	$ 1,434.0	$ 1,518.9	$ 1,468.4	$ 1,431.3	$ 5,741.7	$ 5,852.6	$ 3,665.3
Operating Segments
Revenue from External Customer [Line Items]
Segment sales to external customers									5,741.7	5,852.6	3,665.3	[1]
Operating Segments | Packaging
Revenue from External Customer [Line Items]
Segment sales to external customers									4,477.3	4,540.3	3,431.7	[1]
Operating Segments | Paper
Revenue from External Customer [Line Items]
Segment sales to external customers									1,143.1	1,201.4	216.9	[1]
Operating Segments | Paper | White Papers
Revenue from External Customer [Line Items]
Segment sales to external customers									1,089.6	1,138.5	207.0
Operating Segments | Paper | Market Pulp
Revenue from External Customer [Line Items]
Segment sales to external customers									53.5	62.9	9.9
Operating Segments | Corporate and Other
Revenue from External Customer [Line Items]
Segment sales to external customers									$ 121.3	$ 110.9	$ 16.7

[1] On October 25, 2013, we acquired Boise Inc. (Boise). Our financial results include Boise subsequent to acquisition.