Pension and Other Postretirement Benefit Plans (Narrative) (Details) - USD ($) $ in Millions		12 Months Ended
	Sep. 15, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Company match percentage		7.00%
Contributions		$ 84	$ 81	$ 82
Employer contribution	$ 358
Discretionary contributions by employer	$ 350
Other Postretirement Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Decrease in postretirement obligations		15	(4)
Postretirement benefit expense		(7)	(22)	(23)
Transfer of liabilities		0	0
Employer contribution		$ 28	36
United States Pension Benefits | Postretirement Health Coverage
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service requirement		10 years
Plan, age requirement		55 years
United States Pension Benefits | Pension Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Decrease in postretirement obligations		$ 0	0
Postretirement benefit expense		(2)	0	$ (8)
Transfer of liabilities		0	0
Employer contribution		$ 37	$ 380
United States Pension Benefits | Pension Benefits | Equity Securities
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Target plan asset allocations		24.00%
United States Pension Benefits | Pension Benefits | Fixed Income Funds
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Target plan asset allocations		74.00%
United States Pension Benefits | Pension Benefits | Alternative Investments
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Target plan asset allocations		2.00%