Derivatives And Risk Management Derivatives and Risk Management (Collateral) (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Derivative [Line Items]
Liability position at aggregate fair value	$ 6,684	$ 12,911
Additional Collateral, Aggregate Fair Value	6,682	16,227
Derivative, Fair Value, Amount Offset Against Collateral, Net	38,762	44,390
Commodity Contracts [Member]
Derivative [Line Items]
Letters of credit outstanding	20,000	14,500
Derivative, Fair Value, Amount Offset Against Collateral, Net	16,362	15,510
Collateral Already Posted, Aggregate Fair Value	27,953	20,565
Interest Rate Swap [Member]
Derivative [Line Items]
Letters of credit outstanding	7,200	10,900
Derivative, Fair Value, Amount Offset Against Collateral, Net	22,400	28,880
Collateral Already Posted, Aggregate Fair Value	$ 22,400	$ 28,880