Quarterly Financial Data (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Quarterly Financial Data [Line Items]
Net sales	$ 311.3	$ 319.9	$ 328.9	$ 337.4	$ 314.0	$ 335.5	$ 345.2	$ 365.4	$ 1,297.5		$ 1,360.1		$ 1,301.3
Cost of products sold, excluding depreciation and amortization and other items	254.3	259.5	261.5	263.6	264.8	268.9	284.4	298.1	1,038.9		1,116.2		1,129.0
Unrealized (gains) losses on derivative instruments	(4.1)	(1.5)	4.2	0.7	0.1	(12.3)	0.1	(3.1)	(0.7)		(15.2)		29.9
Gross Profit	61.1	61.9	63.2	73.1	49.1	78.9	60.7	70.4
Operating income	41.6	41.6	40.1	50.0	23.9	56.2	39.6	46.2	173.3		165.9		55.0
Net income	$ 27.3	$ 25.4	$ 18.6	$ 33.5	$ 9.1	$ 29.2	$ 21.0	$ 26.5	$ 104.8		$ 85.8		$ 25.1
Earnings per common share, Basic:
Net income per share	$ 1.48	$ 1.37	$ 0.99	$ 1.75	$ 0.48	$ 1.52	$ 1.10	$ 1.39	$ 5.56		$ 4.49		$ 1.32
Earnings per common share, Diluted:
Net income per share	$ 1.44	$ 1.34	$ 0.98	$ 1.73	$ 0.47	$ 1.51	$ 1.09	$ 1.38	$ 5.44	[1],[2]	$ 4.45	[1],[2]	$ 1.32	[1],[2]
High
Common stock market price:
Common stock market price (based on daily closing price)	$ 73.03	$ 71.96	$ 65.44	$ 65.03	$ 61.75	$ 59.15	$ 52.57	$ 52.46
Low
Common stock market price:
Common stock market price (based on daily closing price)	$ 65.23	$ 62.31	$ 58.75	$ 60.77	$ 56.27	$ 49.42	$ 46.62	$ 46.82

[1] The diluted weighted-average number of common shares outstanding and diluted earnings per share for 2013 and 2012 were calculated using the treasury method. The diluted weighted-average number of common shares outstanding and diluted earnings per share for 2011 were calculated using the two-class method (see Note 1).

[2] Diluted weighted-average number of common shares outstanding and diluted earnings per share for 2013 and 2012 are based on the treasury method. Diluted weighted-average number of common shares outstanding and diluted earnings per share for 2011 is based on the two-class method (see Note 1 and Note 13).