Fair Value Measurements: Balance Sheet Offsetting (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Derivative Asset [Abstract]
Derivative Asset, Fair Value, Gross Asset	$ 16,378	$ 17,546
Gross Amounts Offset In Statement Of Financial Position Assets	(12,937)	(17,546)
Derivative Asset	3,441	0
Derivative Liability [Abstract]
Derivative Liability, Fair Value, Gross Liability	28,132	25,796
Gross Amounts Offset In Statement Of Financial Position Liabilities	(25,141)	(19,776)
Derivative Liability	2,991	6,020
Contract Subject to Master Netting Arrangement [Member]
Derivative Asset [Abstract]
Derivative Asset, Fair Value, Gross Asset	16,378	17,546
Gross Amounts Offset In Statement Of Financial Position Assets	(12,937)	(17,546)
Derivative Asset	3,441	0
Derivative Liability [Abstract]
Derivative Liability, Fair Value, Gross Liability	28,132	19,776
Gross Amounts Offset In Statement Of Financial Position Liabilities	(25,141)	(19,776)
Derivative Liability	2,991	0
Contract Subject to Master Netting Arrangement [Member] \| Interest Rate Swap [Member]
Derivative Asset [Abstract]
Derivative Asset, Fair Value, Gross Asset	3,441
Gross Amounts Offset In Statement Of Financial Position Assets	0
Derivative Asset	3,441
Derivative Liability [Abstract]
Derivative Liability, Fair Value, Gross Liability	2,991	0
Gross Amounts Offset In Statement Of Financial Position Liabilities	0	0
Derivative Liability	2,991	0
Contract Not Subject to Master Netting Arrangement [Member]
Derivative Asset [Abstract]
Derivative Asset, Fair Value, Gross Asset	0	0
Gross Amounts Offset In Statement Of Financial Position Assets	0	0
Derivative Asset	0	0
Derivative Liability [Abstract]
Derivative Liability, Fair Value, Gross Liability	0	6,020
Gross Amounts Offset In Statement Of Financial Position Liabilities	0	0
Derivative Liability	0	6,020
Contract Not Subject to Master Netting Arrangement [Member] \| Interest Rate Swap [Member]
Derivative Asset [Abstract]
Derivative Asset, Fair Value, Gross Asset	0
Gross Amounts Offset In Statement Of Financial Position Assets	0
Derivative Asset	0
Derivative Liability [Abstract]
Derivative Liability, Fair Value, Gross Liability	0	6,020
Gross Amounts Offset In Statement Of Financial Position Liabilities	0	0
Derivative Liability	0	6,020
Crude Oil [Member] \| Contract Subject to Master Netting Arrangement [Member] \| Basis Swap [Member]
Derivative Asset [Abstract]
Derivative Asset, Fair Value, Gross Asset	6,309	8,599
Gross Amounts Offset In Statement Of Financial Position Assets	(6,309)	(8,599)
Derivative Asset	0	0
Derivative Liability [Abstract]
Derivative Liability, Fair Value, Gross Liability	0	0
Gross Amounts Offset In Statement Of Financial Position Liabilities	0	0
Derivative Liability	0	0
Crude Oil [Member] \| Contract Subject to Master Netting Arrangement [Member] \| Commodity Option [Member]
Derivative Asset [Abstract]
Derivative Asset, Fair Value, Gross Asset	0	0
Gross Amounts Offset In Statement Of Financial Position Assets	0	0
Derivative Asset	0	0
Derivative Liability [Abstract]
Derivative Liability, Fair Value, Gross Liability	0	0
Gross Amounts Offset In Statement Of Financial Position Liabilities	0	0
Derivative Liability	0	0
Crude Oil [Member] \| Contract Not Subject to Master Netting Arrangement [Member] \| Basis Swap [Member]
Derivative Asset [Abstract]
Derivative Asset, Fair Value, Gross Asset	0	0
Gross Amounts Offset In Statement Of Financial Position Assets	0	0
Derivative Asset	0	0
Derivative Liability [Abstract]
Derivative Liability, Fair Value, Gross Liability	0	0
Gross Amounts Offset In Statement Of Financial Position Liabilities	0	0
Derivative Liability	0	0
Crude Oil [Member] \| Contract Not Subject to Master Netting Arrangement [Member] \| Commodity Option [Member]
Derivative Asset [Abstract]
Derivative Asset, Fair Value, Gross Asset	0	0
Gross Amounts Offset In Statement Of Financial Position Assets	0	0
Derivative Asset	0	0
Derivative Liability [Abstract]
Derivative Liability, Fair Value, Gross Liability	0	0
Gross Amounts Offset In Statement Of Financial Position Liabilities	0	0
Derivative Liability	0	0
Natural Gas [Member] \| Contract Subject to Master Netting Arrangement [Member] \| Basis Swap [Member]
Derivative Asset [Abstract]
Derivative Asset, Fair Value, Gross Asset	4,335	6,558
Gross Amounts Offset In Statement Of Financial Position Assets	(4,335)	(6,558)
Derivative Asset	0	0
Derivative Liability [Abstract]
Derivative Liability, Fair Value, Gross Liability	556	473
Gross Amounts Offset In Statement Of Financial Position Liabilities	(556)	(473)
Derivative Liability	0	0
Natural Gas [Member] \| Contract Not Subject to Master Netting Arrangement [Member] \| Basis Swap [Member]
Derivative Asset [Abstract]
Derivative Asset, Fair Value, Gross Asset	0	0
Gross Amounts Offset In Statement Of Financial Position Assets	0	0
Derivative Asset	0	0
Derivative Liability [Abstract]
Derivative Liability, Fair Value, Gross Liability	0	0
Gross Amounts Offset In Statement Of Financial Position Liabilities	0	0
Derivative Liability	0	0
Natural Gas, Distribution [Member] \| Contract Subject to Master Netting Arrangement [Member] \| Purchase Contract [Member]
Derivative Asset [Abstract]
Derivative Asset, Fair Value, Gross Asset	2,293	2,389
Gross Amounts Offset In Statement Of Financial Position Assets	(2,293)	(2,389)
Derivative Asset	0	0
Derivative Liability [Abstract]
Derivative Liability, Fair Value, Gross Liability	24,585	19,303
Gross Amounts Offset In Statement Of Financial Position Liabilities	(24,585)	(19,303)
Derivative Liability	0	0
Natural Gas, Distribution [Member] \| Contract Not Subject to Master Netting Arrangement [Member] \| Purchase Contract [Member]
Derivative Asset [Abstract]
Derivative Asset, Fair Value, Gross Asset	0	0
Gross Amounts Offset In Statement Of Financial Position Assets	0	0
Derivative Asset	0	0
Derivative Liability [Abstract]
Derivative Liability, Fair Value, Gross Liability	0	0
Gross Amounts Offset In Statement Of Financial Position Liabilities	0	0
Derivative Liability	$ 0	$ 0

The gross amount of assets offset to determine the net amounts presented in the statement of financial position.

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The gross amount of liabilities offset to determine the net amounts presented in the statement of financial position

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Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

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