Pension and Other Postretirement Benefits (details) (USD $) In Thousands, unless otherwise specified	3 Months Ended				9 Months Ended				12 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013		Dec. 31, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2012
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Accumulated other comprehensive loss	$ (5,861)		$ (8,594)		$ (5,861)		$ (8,594)		$ (6,358)	$ (6,027)	$ (8,826)	$ (9,291)
Other Comprehensive Income (Loss), Amortization, Pension and Other Postretirement Benefit Plans, Net Prior Service Cost Recognized in Net Periodic Benefit Cost, before Tax	(1)		(1)		(5)		(5)
Other Comprehensive Income (Loss), Reclassification, Pension and Other Postretirement Benefit Plans, Net Gain (Loss) Recognized in Net Periodic Benefit Cost, before Tax	275		385		826		1,156
Other Comprehensive Income Total Reclassifications Before Tax	274		384		821		1,151
Other Comprehensive Income (Loss), Amortization, Pension and Other Postretirement Benefit Plans, Net Prior Service Cost Recognized in Net Periodic Pension Cost, Tax	(108)		(152)		(324)		(454)
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax	166		232		497		697
General Discussion of Pension and Other Postretirement Benefits [Abstract]
Qualified Defined Benefit Pension Plan Contributions					10,500
Future reduction in pension contributions for next 10 years					55,000
Multiemployer Plans, Withdrawal Obligation									8,300
Multiemployer Plans, Withdrawal Payment Per Year For Next 20 Years									600
Multiemployer Plan, Withdrawal Liability Cost					8,100
Defined Contribution Plan, Cost Recognized					2,800		2,300
Pension Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract]
Defined Benefit Plan, Service Cost	1,919		2,341		5,755		7,023
Defined Benefit Plan, Interest Cost	4,511		4,103		13,535		12,310
Defined Benefit Plan Expected Return On Plan Assets	(4,887)		(4,678)		(14,659)		(14,034)
Defined Benefit Plan Amortization Of Net Actuarial Loss	2,579		4,421		7,739		13,263
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	56		56		168		167
Defined Benefit Plan Net Periodic Benefit Cost	4,178		6,243		12,538		18,729
Defined Benefit Plan Amount Allocated To Construction	(1,242)		(1,910)		(3,644)		(5,566)
Defined Benefit Plan Net Amount Deferred To Regulatory Balancing Account	(1,107)	[1]	(2,230)	[1]	(3,331)	[1]	(6,850)	[1]
Defined Benefit Plan Net Amount Charged To Expense	1,829		2,103		5,563		6,313
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract]
Defined Benefit Plan, Service Cost	136		178		407		536
Defined Benefit Plan, Interest Cost	309		286		928		858
Defined Benefit Plan Expected Return On Plan Assets	0		0		0		0
Defined Benefit Plan Amortization Of Net Actuarial Loss	46		169		138		507
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	50		50		148		148
Defined Benefit Plan Net Periodic Benefit Cost	541		683		1,621		2,049
Defined Benefit Plan Amount Allocated To Construction	(177)		(226)		(518)		(656)
Defined Benefit Plan Net Amount Deferred To Regulatory Balancing Account	0	[1]	0	[1]	0	[1]	0	[1]
Defined Benefit Plan Net Amount Charged To Expense	$ 364		$ 457		$ 1,103		$ 1,393

[1] The deferral of certain pension expenses above or below the amount set in rates was approved by the OPUC, with recovery of these deferred amounts through the implementation of a balancing account, which includes the expectation of lower net periodic benefit costs in future years. Deferred pension expense balances include accrued interest at the utility’s actual cost of long-term debt, with deferred revenue in the utility's allocated share of equity to be recognized in a future accounting period when deferred pension expense is collected.