Statements of Consolidated Comprehensive Income (Unaudited) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 25.4	$ 21.7	$ 72.6	$ 68.1
Other comprehensive (loss) income, net of tax:
Defined benefit pension plan and Salaried VEBA	1.2	1.1	3.4	3.5
Available for sale securities	0.1	(0.2)	(0.2)	(0.5)
Cash flow hedges	(2.2)	(1.7)	2.4	(5.7)
Other comprehensive (loss) income, net of tax	(0.9)	(0.8)	5.6	(2.7)
Comprehensive income	$ 24.5	$ 20.9	$ 78.2	$ 65.4