Three months ended March 31,

Qualified and Non-qualified

Pension Benefits

Postretirement

United States

International

Benefits

(Millions)

2012

2011

2012

2011

2012

2011

Net periodic benefit cost (benefit)

Service cost

$

63

$

51

$

31

$

28

$

19

$

15

Interest cost

147

158

61

62

22

23

Expected return on plan assets

(248

)

(232

)

(73

)

(70

)

(21

)

(19

)

Amortization of transition (asset) obligation

—

(1

)

—

Amortization of prior service cost (benefit)

2

3

(4

)

(3

)

(18

)

(18

)

Amortization of net actuarial (gain) loss

117

83

30

28

27

26

Net periodic benefit cost (benefit)

$

81

$

63

$

44

$

45

$

29

$

27

Settlements, curtailments, special termination benefits and other

26

—

Net periodic benefit cost (benefit) after settlements, curtailments, special termination benefits and other

$

107

$

63

$

44

$

45

$

29

$

27