CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Unaudited) Parenthetical (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Pension Plan and Restoration of Retirement Income Plan:
Amortization of deferred net loss	$ 0.6	$ 0.4	$ 1.8	$ 1.3
Amortization of prior service cost	0	0	0	0.1
Postretirement Benefit Plans:
Amortization of deferred net loss	0.3	0.2	0.9	0.8
Amortization of deferred net transition obligation	0	0.1	0	0.1
Amortization of prior service cost	(0.3)	(0.3)	(0.8)	(0.8)
Deferred commodity contracts hedging gains reclassified in net income	0.3	0	0.2	(1.6)
Deferred commodity contracts hedging losses	0	(0.3)	0	(0.5)
Amortization of deferred interest rate swap hedging losses	$ 0	$ 0	$ 0.1	$ 0.1