Statements of Consolidated Comprehensive Income (USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2014		Jun. 30, 2013		Jun. 30, 2014		Jun. 30, 2013
Statement of Comprehensive Income [Abstract]
Net income	$ 24.5		$ 18.6		$ 40.3		$ 52.1
Reclassification adjustments:
Amortization of net actuarial (gain) loss	(0.6)	[1]	0.4	[1]	(0.9)	[1]	0.7	[1]
Amortization of prior service cost	2.6	[1]	1.0	[1]	5.4	[1]	2.1	[1]
Other comprehensive income relating to VEBAs	2.0		1.4		4.5		2.8
Available for sale securities:
Unrealized gain on available for sale securities	0.2		0.2		0.3		0.5
Reclassification adjustments:
Reclassification of unrealized gain upon sale of available for sale securities	(0.1)	[2]	(0.2)	[2]	(0.2)	[2]	(0.6)	[2]
Other comprehensive income (loss) relating to available for sale securities	0.1		0		0.1		(0.1)
Foreign currency translation adjustment	(0.1)		0.4		0.1		0.8
Other comprehensive income, before tax	2.0		1.8		4.7		3.5
Income tax expense related to items of other comprehensive income	0.1	[3]	(0.5)	[3]	(1.7)	[3]	(1.0)	[3]
Other comprehensive income, net of tax	2.1		1.3		3.0		2.5
Comprehensive income	$ 26.6		$ 19.9		$ 43.3		$ 54.6

[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.