Consolidated Statements of Income and Comprehensive Income - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Income Statement [Abstract]
Net sales	$ 1,733.7	$ 1,690.6
Cost of sales	(1,312.3)	(1,334.5)
Gross profit	421.4	356.1
Selling, general and administrative expenses	(140.0)	(134.9)
Other expense, net	(6.0)	(8.3)
Income from operations	275.4	212.9	[1]
Non-operating pension expense	(2.0)	(0.5)
Interest expense, net	(24.1)	(25.8)
Income before taxes	249.3	186.6	[1]
Provision for income taxes	(62.5)	(46.5)
Net income	$ 186.8	$ 140.1
Net income per common share:
Basic	$ 1.98	$ 1.48
Diluted	1.97	1.48
Dividends declared per common share	$ 0.79	$ 0.63
Statements of Comprehensive Income:
Net income	$ 186.8	$ 140.1
Foreign currency translation adjustment		(0.1)
Reclassification adjustments to cash flow hedges included in net income, net of tax of $0.3 million and $0.4 million	1.0	1.0
Amortization of pension and postretirement plans actuarial loss and prior service cost, net of tax of $0.8 million and $1.0 million	2.3	3.0
Other comprehensive income	3.3	3.9
Comprehensive income	$ 190.1	$ 144.0

[1] Includes $0.6 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.