Defined Benefit Pension and Other Postretirement Plans
 3 Months Ended
Mar. 31, 2018
Retirement Benefits [Abstract]  
Defined Benefit Pension and Other Postretirement Plans
Defined Benefit Pension and Other Postretirement Plans
The following summarizes the components of net periodic benefit costs:
 
Three Months Ended March 31,
 
Pension Benefits
 
Other Benefits
(In millions)
2018
 
2017
 
2018
 
2017
Components of net periodic benefit cost:
 
 
 
 
 
 
 
Service cost
$
36

 
$
31

 
$
7

 
$
7

Interest cost
18

 
19

 
7

 
8

Expected return on plan assets
(26
)
 
(26
)
 
—

 
—

Amortization – prior service credit
(8
)
 
(10
)
 
(1
)
 
(1
)
                      – actuarial loss
9

 
9

 
—

 
—

                      – settlement loss
1

 
—

 
—

 
—

Net periodic benefit cost
$
30

 
$
23

 
$
13

 
$
14

The components of net periodic benefit cost other than the service cost component are included in the line item “Net interest and other financial costs” in the income statement.
During the three months ended March 31, 2018, we made no contributions to our funded pension plans. Benefit payments related to unfunded pension and other postretirement benefit plans were $6 million and $8 million, respectively, during the three months ended March 31, 2018.