XML 94 R42.htm IDEA: XBRL DOCUMENT v3.20.4
Summary of Significant Accounting Policies - Turnaround Expenses (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Petroleum Segment      
Planned Major Maintenance Activities [Line Items]      
Amortization period 4 years    
Turnaround costs capitalized $ 155 $ 38 $ 8
Petroleum Segment | Minimum      
Planned Major Maintenance Activities [Line Items]      
Frequency of planned major maintenance activities 4 years    
Petroleum Segment | Maximum      
Planned Major Maintenance Activities [Line Items]      
Frequency of planned major maintenance activities 5 years    
Nitrogen Fertilizer Segment      
Planned Major Maintenance Activities [Line Items]      
Turnaround expenses incurred $ 1 $ 10 $ 6
Nitrogen Fertilizer Segment | Minimum      
Planned Major Maintenance Activities [Line Items]      
Frequency of planned major maintenance activities 2 years    
Nitrogen Fertilizer Segment | Maximum      
Planned Major Maintenance Activities [Line Items]      
Frequency of planned major maintenance activities 3 years