Risk Management Activities: Hedging Activities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Amount of Gain/(Loss) on Derivatives Recognized in Income	$ 0	$ 0	$ 17,267
Cash Flow Hedging [Member]
Summary of Cash Flow Hedge Activity [Abstract]
Derivative Instruments, Gain Recognized in Other Comprehensive Income (Loss), Effective Portion	12,670	14,145	6,979
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(10,813)	5,664	6,062
Derivative Instruments, Gain (Loss) Recognized in Income, Ineffective Portion and Amount Excluded from Effectiveness Testing, Net	0	0	0
Cash Flow Hedging [Member] | Interest Rate Swap [Member]
Summary of Cash Flow Hedge Activity [Abstract]
Derivative Instruments, Gain Recognized in Other Comprehensive Income (Loss), Effective Portion	2,888	(536)	7,935
Derivative Instruments, Gain (Loss) Recognized in Income, Ineffective Portion and Amount Excluded from Effectiveness Testing, Net	0	0	0
Cash Flow Hedging [Member] | Interest Rate Swap [Member] | Interest Expense [Member]
Summary of Cash Flow Hedge Activity [Abstract]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	3,647	3,669	6,989
Cash Flow Hedging [Member] | Commodity derivatives [Member]
Summary of Cash Flow Hedge Activity [Abstract]
Derivative Instruments, Gain Recognized in Other Comprehensive Income (Loss), Effective Portion	9,782	14,681	(956)
Cash Flow Hedging [Member] | Commodity derivatives [Member] | Sales Revenue, Goods, Net [Member]
Summary of Cash Flow Hedge Activity [Abstract]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(14,460)	1,995	(927)
Derivative Instruments, Gain (Loss) Recognized in Income, Ineffective Portion and Amount Excluded from Effectiveness Testing, Net	0	0	0
Not Designated as Hedging Instrument [Member] | Interest Rate Swap [Member] | Unrealized Gain Loss on Interest Rate Swaps [Member]
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Amount of Gain/(Loss) on Derivatives Recognized in Income	0	0	30,169	[1]
Not Designated as Hedging Instrument [Member] | Interest Rate Swap [Member] | Interest Expense [Member]
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Amount of Gain/(Loss) on Derivatives Recognized in Income	$ 0	$ 0	$ (12,902)	[1]

[1] These interest rate swaps were settled in the fourth quarter of 2013.