Consolidated Statements of Income and Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014		Dec. 31, 2013
Income Statement [Abstract]
Net sales	$ 5,741.7	$ 5,852.6		$ 3,665.3
Cost of sales	(4,533.7)	(4,623.1)		(2,797.8)
Gross profit	1,208.0	1,229.5		867.5
Selling, general, and administrative expenses	(451.3)	(469.5)		(326.6)
Other expense, net	(6.7)	(57.3)		(59.0)
Income from operations	750.0	702.7		481.9	[1]
Interest expense, net	(85.5)	(88.4)	[2]	(58.3)	[1],[3]
Income before taxes	664.5	614.3		423.6	[1]
(Provision) benefit for income taxes	(227.7)	(221.7)		17.7
Net income	$ 436.8	$ 392.6		$ 441.3
Net income per common share
Basic (US$ per share)	$ 4.47	$ 3.99		$ 4.57
Diluted (US$ per share)	4.47	3.99		4.52
Dividends declared per common share (US$ per share)	$ 2.20	$ 1.60		$ 1.51
Statement of Comprehensive Income:
Net income	$ 436.8	$ 392.6		$ 441.3
Foreign currency translation adjustment	2.7	(2.6)		(0.1)
Reclassification adjustments to cash flow hedges included in net income, net of tax of $2.2 million, $2.2 million, and $2.2 million for 2015, 2014, and 2013, respectively	3.5	3.5		3.5
Amortization of pension and postretirement plans actuarial loss and prior service cost, net of tax of $5.6 million, $2.8 million, and $8.5 million for 2015, 2014, and 2013, respectively	8.8	4.2		13.4
Changes in unfunded employee benefit obligations, net of tax of $8.9 million, $59.2 million, and $20.4 million for 2015, 2014, and 2013, respectively	14.0	(94.0)		32.2
Other comprehensive income (loss)	29.0	(88.9)		49.0
Comprehensive income	$ 465.8	$ 303.7		$ 490.3

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

[2] Includes $1.5 million of expense related to the write-off of deferred financing costs in connection with the debt refinancing discussed in Note 10, Debt.

[3] Includes $10.5 million of expenses for financing the Boise acquisition and $1.1 million of expense for the write-off of deferred financing costs.