Restatement of Previously Issued Financial Statements (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended			6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011		Jun. 30, 2012	Jun. 30, 2011
Statements of Consolidated Income:
Selling, administrative, research and development, and general	$ 14.4	$ 18.0		$ 32.3	$ 33.6
Total costs and expenses	305.6	324.1		624.8	626.9
Operating income	39.6	14.7		85.8	34.5
Income before income taxes	34.2	6.9		77.0	23.9
Income tax provision	(13.2)	(2.8)		(29.5)	(9.0)
Net income	21.0	4.1	[1]	47.5	14.9	[1]
Earnings per common share, Basic:
Net income per share	$ 1.10	$ 0.22		$ 2.49	$ 0.79
Earnings per common share, Diluted:
Net income per share	$ 1.09	$ 0.21		$ 2.48	$ 0.78	[2]
Statements of Consolidated Comprehensive Income:
Net income	21.0	4.1	[1]	47.5	14.9	[1]
Reclassification adjustments:
Amortization of net actuarial loss	0.7	0.2		1.5	0.3
Less: tax impact on amortization of net actuarial loss	(0.3)	(0.1)		(0.6)	(0.1)
Amortization of prior service cost	1.1	1.1		2.1	2.1
Less: tax impact on amortization of prior service cost	(0.4)	(0.4)		(0.8)	(0.8)
Other comprehensive (loss) income, net of tax	1.5	0.8		2.6	1.2
Comprehensive income	22.5	4.9		50.1	16.1
Statements of Consolidated Cash Flows:
Net income	21.0	4.1	[1]	47.5	14.9	[1]
Deferred income taxes				28.9	8.2
Non-cash net periodic benefit income				(6.0)	(3.0)	[3]
Other non-cash charges				0.7	0.2
Previously Reported
Statements of Consolidated Income:
Selling, administrative, research and development, and general		17.3			32.2
Total costs and expenses		323.4			625.5
Operating income		15.4			35.9
Income before income taxes		7.6			25.3
Income tax provision		(3.1)			(9.5)
Net income		4.5			15.8	[1]
Earnings per common share, Basic:
Net income per share		$ 0.24			$ 0.83
Earnings per common share, Diluted:
Net income per share		$ 0.24			$ 0.83	[2]
Statements of Consolidated Comprehensive Income:
Net income		4.5			15.8	[1]
Reclassification adjustments:
Amortization of net actuarial loss					0	[1]
Less: tax impact on amortization of net actuarial loss					0
Amortization of prior service cost					0	[1]
Less: tax impact on amortization of prior service cost					0	[1]
Other comprehensive (loss) income, net of tax					(0.3)	[1]
Comprehensive income					15.5	[1]
Statements of Consolidated Cash Flows:
Net income		4.5			15.8	[1]
Deferred income taxes					8.7
Non-cash net periodic benefit income					(4.4)	[3]
Adjustment
Statements of Consolidated Income:
Selling, administrative, research and development, and general		0.7			1.4
Total costs and expenses		0.7			1.4
Operating income		(0.7)			(1.4)
Income before income taxes		(0.7)			(1.4)
Income tax provision		0.3			(0.5)
Net income		(0.4)			(0.9)	[1]
Earnings per common share, Basic:
Net income per share		$ (0.02)			$ (0.04)
Earnings per common share, Diluted:
Net income per share		$ (0.02)			$ (0.04)	[2]
Statements of Consolidated Comprehensive Income:
Net income		(0.4)			(0.9)	[1]
Reclassification adjustments:
Amortization of net actuarial loss					0.3	[1]
Less: tax impact on amortization of net actuarial loss					(0.1)
Amortization of prior service cost					2.1	[1]
Less: tax impact on amortization of prior service cost					(0.8)	[1]
Other comprehensive (loss) income, net of tax					1.5	[1]
Comprehensive income					0.6	[1]
Statements of Consolidated Cash Flows:
Net income		(0.4)			(0.9)	[1]
Deferred income taxes					(0.5)
Non-cash net periodic benefit income					$ 1.4	[3]

[1] Total comprehensive income and components of other comprehensive income (loss) were previously included in the Statement of Stockholders' Equity for interim reporting periods prior to 2012. The Company adopted ASU No. 2011-05, Comprehensive Income (Topic 220): Presentation of Comprehensive Income, beginning with the annual period ended December 31, 2011 and presented the Statement of Comprehensive Income as its own separate statement. As such, the "Previously Reported" column reflects the changes in the presentation.

[2] Beginning 2012, the Company presented diluted earnings per share under the treasury method because it became more dilutive than the diluted earnings per share under the two-class method. As such, restated diluted earnings per share for the quarter and six months ended June 30, 2011 were calculated based on the treasury method to conform to current period presentation. Previously reported diluted earnings per share for the quarter and six months ended June 30, 2011 are based on the two-class method. The "Adjustment" column reflects the difference between restated diluted earnings per share using the two-class method and the previously reported diluted earnings per share.

[3] Non-cash net periodic benefit cost was included within Other non-cash charges in the six months ended June 30, 2011. Such amount has been reclassified from Other non-cash charges to conform to current period presentation.