Assets Held for Sale (Carrying Value of the Major Categories of Assets and Liabilities Reflected as Held for Sale) (Details) $ in Millions	Sep. 30, 2018 USD ($)
Assets Held for Sale [Abstract]
Accounts receivable, net	$ 37
Derivative assets	23
Other current assets	4
Total current assets held for sale	64
Property, plant and equipment, net	748
Long-term derivative assets	11
Other long-term assets	21
Total long-term assets held for sale	780
Accounts payable	62
Taxes payable	31
Derivative liabilities	10
Other current liabilities	13
Total current liabilities held for sale	116
Long-term derivative liabilities	39
Other long-term liabilities	138
Total long-term liabilities held for sale	$ 177