Summary of Significant Accounting Policies Regulatory Assets Disclosure (Details) (USD $)	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011
Accounting Policies [Abstract]
Public Utilities, Property, Plant and Equipment, Disclosure of Composite Depreciation Rate for Plants in Service	2.80%		2.80%		2.80%
Weighted Average Depreciation Rates Transmission Distribution	2.70%
Weighted Average Depreciation Rates Utility Storage	2.20%
Weighted Average Depreciation Rates General Plant	4.30%
Weighted Average Depreciation Rates Intangible Other	4.10%
Public Utilities, Allowance for Funds Used During Construction, Rate	0.30%		0.30%		0.50%
Outstanding Checks In Accounts Payable	$ 2,800,000.0		$ 2,300,000.0
Unbilled Receivables, Current	61,527,000		56,955,000
Senate Bill Four Zero Eight Charge					7,400,000
Inventory - Gas	51,400,000		58,800,000
Inventory - Materials and supplies	9,300,000		8,800,000
Changes In Fair Value As Deferred Regulatory Assets Or Liabilities In Percentage	80% or 90%
Changes In Fair Value Deferred As Income Statement For Contracts Not Qualifying For Hedge Accounting And To Other Comprehensive Income For Contracts Qualifying For Hedge Accounting	20% or 10%
Oregon PGA Deferral Percentage	90.00%		90.00%		90.00%
Washington PGA Deferral Percentage	100.00%		100.00%		100.00%
Deferred Tax Liabilities, Deferred Expense	56,200,000		60,300,000
Regulatory Assets [Line Items]
Regulatory Assets, Noncurrent	369,603,000		382,255,000		367,536,000	362,472,000	362,290,000	364,132,000	325,692,000	323,371,000	343,085,000
Regulatory Assets, Current	22,635,000		52,448,000
Unrealized Loss On Derivatives [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Noncurrent	615,000	[1]	578,000	[1]
Regulatory Assets, Current	1,891,000	[1]	10,796,000	[1]
Pension and Other Postretirement Plans Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Noncurrent	125,855,000	[2]	182,688,000	[2]
Pension Balancing [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Noncurrent	25,713,000	[2]	14,727,000	[2]
Other Regulatory [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Noncurrent	17,217,000	[3]	7,239,000	[3]
Regulatory Assets, Current	20,744,000	[3]	41,652,000	[3]
Income Tax Asset [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Noncurrent	51,814,000		55,879,000
Environmental Restoration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets, Noncurrent	$ 148,389,000	[4]

[1] Unrealized gains or losses on derivatives are non-cash items and, therefore, do not earn a rate of return or a carrying charge. These amounts are recoverable through utility rates as part of the annual PGA mechanism when realized at settlement.

[2] Certain utility pension costs are approved for regulatory deferral, including amounts recorded to the pension balancing account, to mitigate the effects of higher and lower pension expenses. Pension costs that are deferred include an interest component when recognized in net periodic benefit costs. See Note 8.

[3] Other primarily consists of several deferrals and amortizations under other approved regulatory mechanisms. The accounts being amortized typically earn a rate of return or carrying charge.

[4] Environmental costs relate to specific sites approved for regulatory deferral by the OPUC and WUTC. In Oregon, we earn a carrying charge on amounts paid, whereas amounts accrued but not yet paid do not earn a carrying charge until expended. In Washington, a carrying charge related to deferred amounts will be determined in a future proceeding. For further information on environmental matters, see Note 15.