CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Unaudited) Parenthetical (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Pension Plan and Restoration of Retirement Income Plan:
Amortization of deferred net loss	$ 0.5	$ 0.5	$ 0.9	$ 0.9
Amortization of prior service cost	0.1	(0.1)	0.1	0
Postretirement plans:
Amortization of deferred net loss	0.3	0.1	0.6	0.6
Amortization of deferred net transition obligation	0	(0.1)	0	0
Amortization of prior service cost	(0.2)	(0.3)	(0.5)	(0.6)
Prior service credit arising during the period	0	0	0	6.2
Deferred commodity contracts hedging (gains) losses reclassified in net income	0	3.4	(1.7)	6.6
Deferred commodity contracts hedging losses	(0.2)	(0.5)	(0.2)	(2.5)
Deferred interest rate swaps hedging losses reclassified in net income	$ 0	$ 0	$ 0.1	$ 0.1