Retirement Plans (Amounts Recognized on The Consolidated Balance Sheet) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Current liabilities	$ (306)	$ (296)
Noncurrent liabilities	(5,182)	(5,172)
Pension Benefits
Noncurrent assets	69	61
Current liabilities	(181)	(166)
Noncurrent liabilities	(4,829)	(4,825)
Net liability recognized	(4,941)	(4,930)
Other  Post-retirement Benefits
Noncurrent assets	121	94
Current liabilities	(125)	(130)
Noncurrent liabilities	(353)	(347)
Net liability recognized	$ (357)	$ (383)