Derivatives (Narrative) (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2012 Forward Interest Rate Swaps [Member]	Sep. 30, 2012 Commodity Contract [Member]	Sep. 30, 2012 Interest Rate Swap [Member]
Notional Amount of Interest Rate Cash Flow Hedge Derivatives		$ 250.0
Derivative, Fixed Interest Rate		1.80%
Derivative, Notional Amount			$ 14.0
Derivative, Maturity Date		Mar. 15, 2013	Dec. 31, 2012
Interest rate swap duration, minimum				5 years
Interest rate swap duration, maximum				10 years
Non-hedge derivatives immaterial	0
Fair value hedge ineffectiveness	0
Cash flow hedge ineffectiveness	0