Statements of Consolidated Comprehensive Income (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013
Statement of Comprehensive Income [Abstract]
Net income	$ 15.9		$ 25.4		$ 56.2		$ 77.5
Reclassification adjustments:
Amortization of net actuarial (gain) loss	(0.5)	[1]	0.3	[1]	(1.4)	[1]	1.0	[1]
Amortization of prior service cost	2.6	[1]	1.0	[1]	8.0	[1]	3.1	[1]
Other comprehensive income relating to VEBAs	2.1		1.3		6.6		4.1
Available for sale securities:
Unrealized gain on available for sale securities	(0.2)		0.4		0.1		0.9
Reclassification adjustments:
Reclassification of unrealized gain upon sale of available for sale securities	0	[2]	(0.2)	[2]	(0.2)	[2]	(0.8)	[2]
Other comprehensive income (loss) relating to available for sale securities	(0.2)		0.2		(0.1)		0.1
Foreign currency translation adjustment	0.1		(0.3)		0.2		0.5
Other comprehensive income, before tax	2.0		1.2		6.7		4.7
Income tax expense related to items of other comprehensive income	(0.7)	[3]	(0.6)	[3]	(2.4)	[3]	(1.6)	[3]
Other comprehensive income, net of tax	1.3		0.6		4.3		3.1
Comprehensive income	$ 17.2		$ 26.0		$ 60.5		$ 80.6

[1] Amounts reclassified out of Accumulated other comprehensive income relating to VEBA adjustments were included as a component of Net periodic pension benefit income relating to VEBAs.

[2] Amounts reclassified out of Accumulated other comprehensive income relating to sales of available for sale securities were included as a component of Other income (expense), net. The Company uses the specific identification method to determine the amount reclassified out of accumulated other comprehensive income.

[3] Income tax amounts reclassified out of Accumulated other comprehensive income relating to VEBA adjustments and sales of available for sale securities were included as a component of Income tax provision.