Income Taxes - Schedule of Significant Components of Deferred Income Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Assets
Pension Plans	$ 62	$ 71
Other Employee Benefit Plans	96	127
Other	320	426
Total	478	624
Liabilities
Accelerated Depreciation	7,195	7,020
Other	451	565
Total	7,646	7,585
Net Deferred Income Tax Liabilities	$ 7,168	$ 6,961	[1]

[1] Certain prior year data has been reclassified to conform to the current presentation.