Other Comprehensive Income (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2014		Jun. 30, 2013		Jun. 30, 2014		Jun. 30, 2013
Reclassification adjustments, before tax:
Amortization of net actuarial (gain) loss, before tax	$ (0.6)	[1]	$ 0.4	[1]	$ (0.9)	[1]	$ 0.7	[1]
Amortization of prior service cost, before tax	2.6	[1]	1.0	[1]	5.4	[1]	2.1	[1]
Other comprehensive income relating to VEBAs, before tax	2.0		1.4		4.5		2.8
Available for sale securities:
Unrealized gain on available for sale securities, before tax	0.2		0.2		0.3		0.5
Reclassification adjustments, before tax:
Reclassification of unrealized gain upon sale of available for sale securities, before tax	(0.1)	[2]	(0.2)	[2]	(0.2)	[2]	(0.6)	[2]
Other comprehensive income (loss) relating to available for sale securities, before tax	0.1		0		0.1		(0.1)
Foreign currency translation adjustment, before tax	(0.1)		0.4		0.1		0.8
Cumulative tax rate adjustment, before tax	0
Other comprehensive income, before tax	2.0		1.8		4.7		3.5
Reclassification adjustments, income tax (expense) benefit:
Amortization of net actuarial (gain) loss, income tax (expense) benefit	0.2	[1],[3]	(0.1)	[1],[3]	0.3	[1],[3]	(0.2)	[1],[3]
Amortization of prior service cost, income tax (expense) benefit	(1.0)	[1],[3]	(0.4)	[1],[3]	(2.0)	[1],[3]	(0.8)	[1],[3]
Other comprehensive income relating to VEBAs, income tax (expense) benefit	(0.8)	[3]	(0.5)	[3]	(1.7)	[3]	(1.0)	[3]
Available for sale securities:
Unrealized gain on available for sale securities, Income tax (expense) benefit	(0.1)	[3]	(0.1)		(0.1)	[3]	(0.2)	[3]
Reclassification adjustments, income tax (expense) benefit:
Reclassification of unrealized gain upon sale of available for sale securities, income tax (expense) benefit	0.1	[2],[3]	0.1	[2],[3]	0.1	[2],[3]	0.2	[2],[3]
Other comprehensive income (loss) relating to available for sale securities, income tax (expense) benefit	0	[3]	0	[3]	0	[3]	0	[3]
Foreign currency translation adjustment, income tax (expense) benefit	0	[3]	0	[3]	0	[3]	0	[3]
Cumulative tax rate adjustment, tax	0.9	[3]
Other comprehensive income, Income tax (expense) benefit	0.1	[3]	(0.5)	[3]	(1.7)	[3]	(1.0)	[3]
Reclassification adjustments, net of tax:
Amortization of net actuarial (gain) loss, net of tax	(0.4)	[1]	0.3	[1]	(0.6)	[1]	0.5	[1]
Amortization of prior service cost, net of tax	1.6	[1]	0.6	[1]	3.4	[1]	1.3	[1]
Other comprehensive income relating to VEBAs, net of tax	1.2		0.9		2.8		1.8
Available for sale securities:
Unrealized gain on available for sale securities, net of tax	0.1		0.1		0.2		0.3
Reclassification adjustments, net of tax:
Reclassification of unrealized gain upon sale of available for sale securities, net of tax	0	[2]	(0.1)	[2]	(0.1)	[2]	(0.4)	[2]
Other comprehensive income (loss) relating to available for sale securities, net of tax	0.1		0		0.1		(0.1)
Foreign currency translation adjustment, net of tax	(0.1)		0.4		0.1		0.8
Cumulative tax rate adjustment, net of tax	0.9
Other comprehensive income, net of tax	$ 2.1		$ 1.3		$ 3.0		$ 2.5

[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.