Consolidated Statements of Income and Comprehensive Income - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Income Statement [Abstract]
Net sales	$ 1,708.7	$ 1,733.7
Cost of sales	(1,343.7)	(1,312.3)
Gross profit	365.0	421.4
Selling, general and administrative expenses	(145.9)	(140.0)
Other expense, net	(10.0)	(6.0)
Income from operations	209.1	275.4
Non-operating pension income (expense)	0.6	(2.0)
Interest expense, net	(19.6)	(24.1)
Income before taxes	190.1	249.3
Provision for income taxes	(48.4)	(62.5)
Net income	$ 141.7	$ 186.8
Net income per common share:
Basic	$ 1.50	$ 1.98
Diluted	1.49	1.97
Dividends declared per common share	$ 0.79	$ 0.79
Statements of Comprehensive Income:
Net income	$ 141.7	$ 186.8
Reclassification adjustments to cash flow hedges included in net income, net of tax of $0.0 million and $0.3 million		1.0
Changes in unrealized losses on marketable debt securities, net of tax of $0.1 million and $0.0 million	(0.2)
Amortization of pension and postretirement plans actuarial loss and prior service cost, net of tax of $0.9 million and $0.8 million	2.7	2.3
Other comprehensive income	2.5	3.3
Comprehensive income	$ 144.2	$ 190.1