Annual report pursuant to Section 13 and 15(d)

Share-Based Compensation - Narrative (Details)

v3.8.0.1
Share-Based Compensation - Narrative (Details) - USD ($)
$ in Millions
 1 Months Ended 12 Months Ended
Jan. 31, 2017
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Accrued liabilities, Share-Based Compensation Obligation   $ 1,078 $ 637  
Restricted Stock Share Awards [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Vesting Period - service years, option 1   1 year    
Vesting Period - service years, option 2   2 years    
Vesting Period - service years, option 3   3 years    
Vesting Period - service years, option 4   4 years    
Vested in Period, Fair Value   $ 78 36 $ 50
Grants in Period, Number of Awards   0    
Restricted Stock Units (RSUs) [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Vesting Period - service years, option 1   2 years    
Vesting Period - service years, option 2   3 years    
Vesting Period - service years, option 3   4 years    
Performance Units [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Award Vesting Period, Cliff Vesting   3 years    
Performance Units [Member] | Minimum [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Percentage of Target Amount Earned Upon Vesting If Threshold Performance is Met   50.00%    
Performance Units [Member] | Maximum [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Percentage of Target Amount Earned Upon Vesting If Threshold Performance is Met   200.00%    
Phantom Unit Awards [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Vesting Period - service years, option 1   2 years    
Vesting Period - service years, option 2   3 years    
Vesting Period - service years, option 3   4 years    
Vested in Period, Fair Value   $ 86 $ 78 $ 50
Grants in Period, Number of Awards   0 1,800,000 5,900,000
Accrued liabilities, Share-Based Compensation Obligation     $ 1  
2003 Stock Incentive Plan [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Number of Shares Authorized   21,000,000    
2011 Incentive Plan [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Number of Shares Authorized   35,000,000    
Number of Additional Shares Authorized 7,800,000      
2015 Inducement Plan [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Number of Shares Authorized   1,000,000    
Number of Shares Granted Plan-to-Date   200,000    
Share-based Payment Award, Number of Shares Available for Grant   0