BENEFITS

The components of our net periodic pension and Other Post-Retirement Employee Benefits (OPEB) costs for the three and six months ended June 30 were as follows:



	Pension Costs
	Three Months Ended June 30						Six Months Ended June 30
Benefit Plan Cost Components	2013			2012			2013			2012
	(Millions of Dollars)
Net Periodic Benefit Cost
Service cost	$	3.1		$	5.4		$	7.3		$	10.8
Interest cost	15.1			16.4			30.2			32.8
Expected return on plan assets	(23.9		)	(22.2		)	(47.9		)	(44.8		)
Amortization of:
Prior service cost	0.6			0.6			1.2			1.2
Actuarial loss	13.6			10.3			27.2			20.2
Net Periodic Benefit Cost	$	8.5		$	10.5		$	18.0		$	20.2



	OPEB Costs
	Three Months Ended June 30						Six Months Ended June 30
Benefit Plan Cost Components	2013			2012			2013			2012
	(Millions of Dollars)
Net Periodic Benefit Cost
Service cost	$	2.3		$	2.4		$	5.0		$	5.2
Interest cost	3.9			5.1			7.8			10.2
Expected return on plan assets	(5.3		)	(4.8		)	(10.6		)	(9.6		)
Amortization of:
Transition obligation	—			0.1			—			0.2
Prior service (credit)	(0.5		)	(0.4		)	(1.0		)	(0.9		)
Actuarial loss	0.9			1.7			1.8			3.5
Net Periodic Benefit Cost	$	1.3		$	4.1		$	3.0		$	8.6

During the first six months of 2013 and 2012, we made no contributions to our qualified benefit plans. Future contributions to the plans will be dependent upon many factors, including the performance of existing plan assets and long-term discount rates.

Postemployment Benefits: Postemployment benefits provided to former or inactive employees are recognized when an event occurs. The estimated liability for such benefits was $4.0 million as of June 30, 2013 and December 31, 2012.