CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME PARENTHETICAL (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Pension Plan and Restoration of Retirement Income Plan:
Amortization of deferred net loss	$ 1.4	$ 1.2	$ 2.0
Net gain (loss) arising during the period	(6.7)	4.4	0.4
Amortization of prior service cost	0.2	0.1	0.1
Prior service cost arising during the period	0	0	(0.2)
Postretirement plans:
Amortization of deferred net loss	(1.6)	0.6	0.7
Net loss arising during the period	(3.1)	(2.4)	(4.1)
Amortization of deferred net transition obligation	0.1	0.1	0.1
Amortization of prior service cost	(1.6)	0.1	0.1
Prior service cost arising during the period	9.5	0	0
Deferred commodity contract hedging losses reclassified in net income	12.6	9.9	4.7
Deferred commodity contracts hedging gains (losses)	(1.7)	(8.5)	(42.6)
Deferred interest rate swaps hedging gains	$ 0.2	$ 0.2	$ 0.2