Pension and Other Postretirement Benefits

Beginning in 2017, the Company changed the method used to estimate the service and interest cost components of net periodic benefit cost related to pension and other postretirement benefit plans. The new method provides a more precise measure of the service and interest cost components of net periodic benefit cost by applying specific spot rates along the yield curve to the projected cash flows rather than a single weighted-average rate. The Company accounted for this change as a change in estimate prospectively. The change did not have a material impact on the 2017 net periodic pension and other postretirement benefit costs.

Pension and other postretirement benefit costs for the three and six months ended June 30, 2017 and 2016 were as follows:



	Three Months Ended												Six Months Ended
	June 30,												June 30,
	Pension						Other Postretirement Benefits						Pension						Other Postretirement Benefits
In millions	2017			2016			2017			2016			2017			2016			2017			2016
Components of net periodic benefit cost:
Service cost	$	16		$	16		$	2		$	3		$	32		$	32		$	4		$	5
Interest cost	18			24			5			6			36			47			10			12
Expected return on plan assets	(33		)	(36		)	(5		)	(5		)	(66		)	(73		)	(11		)	(11		)
Amortization of actuarial loss	14			10			(1		)	—			28			21			(1		)	—
Amortization of prior service income	—			—			—			(1		)	—			—			—			(1		)
Total net periodic benefit cost	$	15		$	14		$	1		$	3		$	30		$	27		$	2		$	5

The Company expects to contribute approximately $179 million to its pension plans and $5 million to its other postretirement plans in 2017. During the six months ended June 30, 2017, the Company made contributions of $170 million to its pension plans, which include an additional $115 million discretionary contribution made in the second quarter of 2017. Contributions of $3 million have been made to other postretirement plans during the six months ended June 30, 2017.