Income Taxes (Deferred Income Tax Assets (Liabilities)) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Pension and other postretirement benefits	$ 239	$ 253
Tax credits and loss carryforwards	477	411
Lease liability	117	104
Other	465	388
Deferred Tax Assets, Gross	1,298	1,156
Valuation allowances	(272)	(248)
Total deferred tax assets	1,026	908
Property, plant and equipment, net	900	795
Investments in subsidiaries	111	103
Goodwill	54	66
Deferred Tax Liabilities, Intangible Assets	159	4
Lease asset	117	105
Other	146	104
Total deferred tax liabilities	1,487	1,177
Net deferred tax assets (liabilities)	$ (461)	$ (269)