Income Taxes (Reconciliation Of Taxes Computed At The Statutory Rate To Income Tax Expense) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Provision for federal income tax, at statutory rate	$ 120	$ 280	$ 378
State income tax provision, net of federal income tax effect	10	28	26
Foreign income tax rate differential	(6)	14	(36)
Manufacturing deduction	0	0	(23)
Depletion	(5)	(4)	(7)
Noncontrolling interests	(8)	(6)	(9)
Tax Act related adjustment	0	0	(591)
Change in valuation allowance	(17)	(9)	3
Changes in state apportionment and other state adjustments	11	(6)	2
Other, net	3	3	(1)
Provision for (benefit from) income taxes	$ 108	$ 300	$ (258)