
8.	EMPLOYEE BENEFIT PLANS

The components of net periodic benefit cost (credit) related to our defined benefit plans were as follows (in millions):



	Pension Plans						Other Postretirement Benefit Plans
	2017			2016			2017			2016
Three months ended September 30:
Service cost	$	31		$	28		$	1		$	2
Interest cost	21			21			3			3
Expected return on plan assets	(37		)	(35		)	—			—
Amortization of:
Net actuarial (gain) loss	13			13			—			(1		)
Prior service credit	(5		)	(5		)	(4		)	(4		)
Special charges (credits)	3			(7		)	—			—
Net periodic benefit cost	$	26		$	15		$	—		$	—

Nine months ended September 30:
Service cost	$	92		$	84		$	4		$	5
Interest cost	64			63			8			9
Expected return on plan assets	(112		)	(104		)	—			—
Amortization of:
Net actuarial (gain) loss	40			37			(2		)	(1		)
Prior service credit	(15		)	(15		)	(12		)	(12		)
Special charges (credits)	3			(7		)	—			—
Net periodic benefit cost (credit)	$	72		$	58		$	(2	)	$	1

We contributed $104 million and $132 million, respectively, to our pension plans and $17 million and $12 million, respectively, to our other postretirement benefit plans during the nine months ended September 30, 2017 and 2016. Of the $104 million contributed to our pension plans during the nine months ended September 30, 2017, $80 million was discretionary and was contributed during the third quarter of 2017.

As a result of the discretionary pension contributions discussed above, our expected contributions to our pension plans have increased to $108 million for 2017. Our anticipated contributions to our other postretirement benefit plans during 2017 have not changed from the amount previously disclosed in our financial statements for the year ended December 31, 2016.