Derivatives (Narrative) (Details) (USD $)	6 Months Ended
	Jun. 30, 2013		Jun. 30, 2012
Derivative Instruments, Gain [Line Items]
Period over which gain included in AOCI will be transferred to earnings, months	12 months
Expected earnings transfer	$ 1,700,000
Expected derivative maturity date	Dec. 31, 2013
Commodity Derivatives [Member]
Derivative Instruments, Gain [Line Items]
Accumulated OCI gain, net of tax	$ 1,709,000	[1]	$ 30,314,000	[1]

[1] Net of taxes.