Summary Of Significant Accounting Policies (Schedule of Inventory) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Accounting Policies [Abstract]
Materials and supplies inventories	$ 75	$ 128
Commodities	130	114
Inventories	205	242
Net materials and supplies inventories reserves	$ 2	$ 5

Amount of valuation reserve for inventory.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant