Short-term Borrowings and Other Debt Obligations (Narrative) (Details)			3 Months Ended			6 Months Ended
	Jun. 15, 2019 USD ($)	Feb. 28, 2018 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)	Mar. 31, 2018
Short-term Debt [Line Items]
Collateralized Agreements			$ 113,000,000			$ 113,000,000
Debt instrument, covenant, senior leverage ratio, period two				2.5
Debt instrument, covenant, specified leverage and letter of credit ratio, period two						3.5
Debt instrument, covenant, asset coverage ratio						4.0
Debt Instrument, Covenant, Initial Current Asset Coverage Ratio						2.1
Bond Tender and Call Premium			0		$ 0	$ 0	$ (34,000,000)
Repayments of Long-term Debt, Long-term Capital Lease Obligations, and Capital Securities						17,000,000	$ 455,000,000
364 Day Secured RCF [Member]
Short-term Debt [Line Items]
Short-term debt			317,000,000			317,000,000		$ 317,000,000
Committed letters of credit
Short-term Debt [Line Items]
Letters of Credit Outstanding, Amount			247,000,000			247,000,000
Domestic and foreign facility
Short-term Debt [Line Items]
Short term borrowings			0			0
Committed Letters of Credit [Member]
Short-term Debt [Line Items]
Letters of Credit Outstanding, Amount			166,000,000			166,000,000
Revolving Credit Facility
Short-term Debt [Line Items]
Credit agreement, maximum capacity			846,000,000			846,000,000
A&R Credit Agreement
Short-term Debt [Line Items]
Credit agreement, maximum capacity			529,000,000			529,000,000
Senior Notes, 9.875 Percent due 2025
Short-term Debt [Line Items]
Long-term Debt		$ 600,000,000
Senior Notes, 9.625% due 2019
Short-term Debt [Line Items]
Long-term Debt		425,000,000
Interest Payable		20,000,000
Repayments of Long-term Debt, Long-term Capital Lease Obligations, and Capital Securities		$ 475,000,000
Term Loan Borrowings before Debt Issuance Cost [Member]
Short-term Debt [Line Items]
Debt and Capital Lease Obligations			298,000,000			298,000,000
Senior Notes
Short-term Debt [Line Items]
Debt Instrument, Periodic Payment, Interest	$ 69,000,000
Senior Notes | Senior Notes, 9.875 Percent due 2025
Short-term Debt [Line Items]
Stated interest rate on debt		9.875%
Senior Notes | Senior Notes, 9.625% due 2019
Short-term Debt [Line Items]
Stated interest rate on debt		9.625%
Senior Notes | Senior Notes, 6.00% due 2018
Short-term Debt [Line Items]
Stated interest rate on debt									6.00%
Extending Lenders | A&R Credit Agreement
Short-term Debt [Line Items]
Credit agreement, maximum capacity			303,000,000			303,000,000
Nonextending Lenders [Member] | A&R Credit Agreement
Short-term Debt [Line Items]
Credit agreement, maximum capacity			226,000,000			$ 226,000,000
London Interbank Offered Rate (LIBOR) | Term Loan Agreement
Short-term Debt [Line Items]
Debt Instrument, Basis Spread on Variable Rate						2.30%
London Interbank Offered Rate (LIBOR) | 364-day credit agreement [Member]
Short-term Debt [Line Items]
Debt Instrument, Basis Spread on Variable Rate						3.05%
London Interbank Offered Rate (LIBOR) | Extending Lenders | Minimum | A&R Credit Agreement
Short-term Debt [Line Items]
Debt Instrument, Basis Spread on Variable Rate						3.55%
London Interbank Offered Rate (LIBOR) | Nonextending Lenders [Member] | Minimum | A&R Credit Agreement
Short-term Debt [Line Items]
Debt Instrument, Basis Spread on Variable Rate						2.80%
Term Loan Agreement | DIP Credit Agreement
Short-term Debt [Line Items]
Debt Instrument, Periodic Payment			$ 12,500,000