Statements of Consolidated Income Statements of Consolidated Income (Parenthetical) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013
Income Statement [Abstract]
Accumulated other comprehensive income reclassifications related to VEBA adjustments	$ 2.1		$ 1.3		$ 6.6		$ 4.1
Reclassification of unrealized gain upon sale of available for sale securities	0	[1]	(0.2)	[1]	(0.2)	[1]	(0.8)	[1]
Other comprehensive income reclassification adjustment, tax	$ (0.8)		$ (0.5)		$ (2.4)		$ (1.3)

[1] 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.