Pension and Other Postretirement Benefits (tables)

9 Months Ended

Sep. 30, 2012

General Discussion of Pension and Other Postretirement Benefits [Abstract]

Net Periodic Benefit Cost Components

	Three Months Ended Three Months Ended September 30,
							Other Postretirement
	Pension Benefits						Benefits
Thousands	2012			2011			2012			2011
Service cost	$	2,130		$	1,839		$	177		$	168
Interest cost	4,303			4,503			314			344
Expected return on plan assets	(4,637		)	(4,455		)	—			—
Amortization of net actuarial loss	3,844			2,683			103			68
Amortization of prior service costs	48			88			50			50
Amortization of transition obligations	—			—			103			103
Net periodic benefit cost	5,688			4,658			747			733
Amount allocated to construction	(1,676		)	(1,279		)	(252		)	(234		)
Amount deferred to regulatory balancing account(1)	(2,111		)	(1,330		)	—			—
Net amount charged to expense	$	1,901		$	2,049		$	495		$	499

	Six Months Ended Nine Months Ended September 30,
							Other Postretirement
	Pension Benefits						Benefits
Thousands	2012			2011			2012			2011
Service cost	$	6,390		$	5,638		$	531		$	504
Interest cost	12,911			13,556			943			1,031
Expected return on plan assets	(13,914		)	(13,367		)	—			—
Amortization of net actuarial loss	11,531			8,067			309			204
Amortization of prior service costs	146			264			148			148
Amortization of transition obligations	—			—			309			309
Net periodic benefit cost	17,064			14,158			2,240			2,196
Amount allocated to construction	(4,522		)	(3,765		)	(681		)	(689		)
Amount deferred to regulatory balancing account(1)	(6,273		)	(3,989		)	—			—
Net amount charged to expense	$	6,269		$	6,404		$	1,559		$	1,507