Borrowings and Other Obligations (Narrative) (Details) - USD ($)	3 Months Ended
	Mar. 31, 2020	Dec. 31, 2019	Dec. 12, 2019
Short-term Debt [Line Items]
Debt instrument, unused borrowing capacity, amount	$ 235,000,000
Credit Facility, Borrowing	100,000,000
A&R Credit Agreement Letters of Credit
Short-term Debt [Line Items]
Letters of credit outstanding, amount	140,000,000
LC Credit Agreement Letters of Credit
Short-term Debt [Line Items]
Letters of credit outstanding, amount	120,000,000
Other short-term bank loans
Short-term Debt [Line Items]
Short-term debt	15,000,000	$ 3,000,000
Committed Letters of Credit
Short-term Debt [Line Items]
Letters of credit outstanding, amount		$ 361,000,000
Letters of credit outstanding, cash collateral	91,000,000
Committed letters of credit
Short-term Debt [Line Items]
Letters of credit outstanding, amount	101,000,000
ABL Credit Agreement
Short-term Debt [Line Items]
Credit agreement, maximum capacity			$ 450,000,000
Long-term line of credit	$ 0
LC Credit Agreement
Short-term Debt [Line Items]
Credit agreement, maximum capacity			$ 195,000,000
Senior Notes | Exit Notes, 11.00 Percent Due 2024
Short-term Debt [Line Items]
Stated interest rate on debt			11.00%
Face amount of debt			$ 2,100,000,000