Short-Term Borrowings, Long-Term Debt and Available Credit Facilities Short-Term Borrowings (Narrative) (Details) - Successor [Member] - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Short-term Debt [Line Items]
Line Of Credit Facility, Remaining Borrowing Capacity, Uncommitted Amount	$ 663
Letters of Credit Outstanding, Amount	$ 172
Short-term Debt, Weighted Average Interest Rate	3.00%	1.80%
Fair Value, Inputs, Level 2 [Member]
Short-term Debt [Line Items]
Short-term Debt, Fair Value	$ 2,160	$ 2,780