Retirement Benefits (Tables)

3 Months Ended

Mar. 31, 2013

Retirement Benefits

Schedule of net periodic benefit pension cost

Net periodic benefit cost, some of which is capitalized as a component of labor cost and some of which is deferred as a regulatory asset, is comprised of the following components and is shown for our noncontributory defined benefit pension plan, our supplemental retirement program (SERP) and other postretirement benefits (OPEB) (in thousands):

	Three months ended March 31,
	Pension						SERP						OPEB
	2013			2012			2013			2012			2013			2012
Service cost	$	1,868		$	1,628		$	15		$	7		$	755		$	565
Interest cost	2,509			2,551			63			56			992			1,032
Expected return on plan assets	(3,125		)	(3,076		)	—			—			(1,099		)	(1,041		)
Amortization of prior service cost (1)	133			133			(2		)	(2		)	(253		)	(253		)
Amortization of net actuarial loss (1)	2,590			1,950			104			76			649			468
Net periodic benefit cost	$	3,975		$	3,186		$	180		$	137		$	1,044		$	771

	Twelve months ended March 31,
	Pension						SERP						OPEB
	2013			2012			2013			2012			2013			2012
Service cost	$	6,500		$	5,830		$	59		$	81		$	2,591		$	2,205
Interest cost	10,215			10,366			270			198			3,996			4,286
Expected return on plan assets	(12,358		)	(11,534		)	—			—			(4,193		)	(4,148		)
Amortization of prior service cost (1)	532			532			(8		)	(8		)	(1,011		)	(1,011		)
Amortization of net actuarial loss (1)	8,576			6,091			416			213			1,844			1,729
Net periodic benefit cost	$	13,465		$	11,285		$	737		$	484		$	3,227		$	3,061

(1) Amounts are amortized from our regulatory asset originally recorded upon recognizing our net pension liability on the balance sheet.