Income Tax Matters, Textuals (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2015	Mar. 31, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Income Tax Contingency
Income tax provision (benefit)	$ 12.6		$ 9.2	$ (151.2)	$ 33.1
Effective tax rate	36.30%		36.70%	37.70%	37.00%
Gross unrecognized tax benefits	$ 1.6			$ 1.6		$ 2.2
Gross unrecognized tax benefits that would impact effective tax rate	0.5			$ 0.5		$ 1.1
Union VEBA
Income Tax Contingency
Income tax benefit on removal of Union VEBA net assets	$ 184.4	$ 184.4