BENEFITS

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



	Pension Costs
	Three Months Ended September 30						Nine Months Ended September 30
Benefit Plan Cost Components	2013			2012			2013			2012
	(Millions of Dollars)
Net Periodic Benefit Cost
Service cost	$	3.7		$	5.5		$	11.0		$	16.3
Interest cost	15.1			16.4			45.3			49.2
Expected return on plan assets	(23.9		)	(22.5		)	(71.8		)	(67.3		)
Amortization of:
Prior service cost	0.5			0.5			1.7			1.7
Actuarial loss	13.6			10.2			40.8			30.4
Net Periodic Benefit Cost	$	9.0		$	10.1		$	27.0		$	30.3



	OPEB Costs
	Three Months Ended September 30						Nine Months Ended September 30
Benefit Plan Cost Components	2013			2012			2013			2012
	(Millions of Dollars)
Net Periodic Benefit Cost
Service cost	$	2.5		$	2.6		$	7.5		$	7.8
Interest cost	3.9			5.1			11.7			15.3
Expected return on plan assets	(5.4		)	(4.8		)	(16.0		)	(14.4		)
Amortization of:
Transition obligation	—			—			—			0.2
Prior service (credit)	(0.5		)	(0.5		)	(1.5		)	(1.4		)
Actuarial loss	1.0			1.9			2.8			5.4
Net Periodic Benefit Cost	$	1.5		$	4.3		$	4.5		$	12.9

During the first nine months of 2013 and 2012, we contributed zero and $100.0 million, respectively, 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 September 30, 2013 and December 31, 2012.