Retirement Plans (Tables)
 12 Months Ended
Dec. 31, 2018
Retirement Benefits [Abstract]  
Schedule of Net Benefit Costs [Table Text Block] The following table presents additional information about our international pension plans.
 
December 31
Millions of dollars
2018
2017
Amounts recognized on the Consolidated Balance Sheets
 
 
Other Assets
$
39

$
2

Accrued employee compensation and benefits
8

15

Employee compensation and benefits
150

267

Pension plans in which projected benefit obligation exceeded plan assets
 
 
Projected benefit obligation (a)
$
176

$
1,202

Fair value of plan assets
18

920

Pension plans in which accumulated benefit obligation exceeded plan assets
 
 
Accumulated benefit obligation (a)
$
105

$
1,139

Fair value of plan assets
18

920
Schedule of Allocation of Plan Assets [Table Text Block] The following table sets forth the fair values of assets held by our international pension plans by level within the fair value hierarchy.
Millions of dollars
Level 1
Level 2
Level 3
Total
Cash and equivalents
$
—

$
12

$
—

$
12

Common/collective trust funds (a)
 
 
 
 
Equity funds (b)
—

137

—

137

Bond funds (c)
—

302

21

323

Alternatives funds (d)
—

209

—

209

Real estate funds (e)
—

81

28

109

Other assets
6

21

15

42

Fair value of plan assets at December 31, 2018
$
6

$
762

$
64

$
832

Cash and equivalents
$
—

$
11

$
—

$
11

Common/collective trust funds (a)
 
 
 
 
Equity funds (b)
—

204

—

204

Bond funds (c)
—

323

46

369

Alternatives fund (d)
—

184

—

184

Real estate funds (e)
—

98

28

126

Other assets
7

22

17

46

Fair value of plan assets at December 31, 2017
$
7

$
842

$
91

$
940


(a) Common/collective trust funds are valued at the net asset value of units held by the plans at year-end.
(b) Strategy is to invest in diversified funds of global common stocks.
(c) Strategy is to invest in diversified funds of fixed income securities of varying geographies and credit quality and whose cash flows approximate the maturities of the benefit obligation.
(d) Strategy is to invest in a fund of diversifying investments, including but not limited to reinsurance, commodities and currencies.
(e) Strategy is to invest in diversified funds of real estate investment trusts and private real estate.
Schedule of Assumptions Used [Table Text Block] Certain weighted-average actuarial assumptions used to determine benefit obligations of our international pension plans at December 31 were as follows:
 
2018
2017
Discount rate
3.3%
2.8%
Rate of compensation increase
5.8%
5.5%

Certain weighted-average actuarial assumptions used to determine net periodic benefit cost of our international pension plans for the years ended December 31 were as follows:
 
2018
2017
2016
Discount rate
2.8%
2.9%
4.2%
Expected long-term return on plan assets
4.1%
4.2%
5.3%
Rate of compensation increase
5.5%
4.8%
5.4%