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Pension Plans and Other Postretirement Benefits - Additional Information (Details)
$ in Millions
12 Months Ended
Sep. 30, 2015
Plan
Dec. 31, 2016
USD ($)
Plan
Dec. 31, 2015
USD ($)
Plan
Dec. 31, 2014
USD ($)
Plan
Compensation and Retirement Disclosure [Abstract]        
Employer's contributions under defined contribution plans   $ 295 $ 251 $ 238
Defined Benefit Plan Disclosure [Line Items]        
Number of defined benefit plans | Plan   7 7 9
Multiemployer Plans, Pension        
Defined Benefit Plan Disclosure [Line Items]        
Period contributions   $ 15 $ 14 $ 14
Pension Plans        
Defined Benefit Plan Disclosure [Line Items]        
Settlement loss   $ 0 $ 0 3
Discount rate   4.00% 4.25%  
Employer contributions   $ 25 $ 22 42
Estimated future employer contributions in next fiscal year   39    
Benefit obligation   844 844 796
Net periodic pension cost   $ 27 $ 19 $ 21
Pension Plans | Level 1        
Defined Benefit Plan Disclosure [Line Items]        
Actual plan asset allocations percent   7.00% 21.00%  
Pension Plans | Level 2        
Defined Benefit Plan Disclosure [Line Items]        
Actual plan asset allocations percent   93.00% 79.00%  
Pension Plans | Fixed Income Securities        
Defined Benefit Plan Disclosure [Line Items]        
Actual plan asset allocations percent   94.00% 79.00%  
Pension Plans | Equity Securities        
Defined Benefit Plan Disclosure [Line Items]        
Actual plan asset allocations percent   5.00% 19.00%  
Pension Plans | Money Market Funds        
Defined Benefit Plan Disclosure [Line Items]        
Actual plan asset allocations percent   1.00% 2.00%  
Pension Plans | Minimum        
Defined Benefit Plan Disclosure [Line Items]        
Settlement loss   $ 175    
Expected long-term rate of return on plan assets   4.00% 5.75%  
Rate of compensation increase   4.00% 4.00%  
Pension Plans | Minimum | Fixed Income Securities        
Defined Benefit Plan Disclosure [Line Items]        
Actual plan asset allocations percent   80.00%    
Pension Plans | Minimum | Equity Securities        
Defined Benefit Plan Disclosure [Line Items]        
Actual plan asset allocations percent   0.00%    
Pension Plans | Maximum        
Defined Benefit Plan Disclosure [Line Items]        
Settlement loss   $ 225    
Expected long-term rate of return on plan assets   5.50% 6.75%  
Rate of compensation increase   6.00% 6.00%  
Pension Plans | Maximum | Fixed Income Securities        
Defined Benefit Plan Disclosure [Line Items]        
Actual plan asset allocations percent   100.00%    
Pension Plans | Maximum | Equity Securities        
Defined Benefit Plan Disclosure [Line Items]        
Actual plan asset allocations percent   20.00%    
Tax Qualified Pension Plans, Defined Benefit        
Defined Benefit Plan Disclosure [Line Items]        
Number of defined benefit plans | Plan 4 2 2 4
Discount rate   3.09% 3.25%  
Unfunded Nonqualified Supplemental Retirement Plans        
Defined Benefit Plan Disclosure [Line Items]        
Number of defined benefit plans | Plan   5 5 5
Other Postretirement Benefit Plan        
Defined Benefit Plan Disclosure [Line Items]        
Period contributions   $ 52 $ 60 $ 58
Benefit obligation   24 33  
Net periodic pension cost   $ 1 $ 2 $ 1