Short-term Borrowings and Other Debt Obligations (Narrative) (Details) - USD ($)		3 Months Ended
	Feb. 28, 2018	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Short-term Debt [Line Items]
Credit agreement, maximum capacity		$ 1,144,000,000
Line of Credit Facility, Remaining Borrowing Capacity		$ 93,000,000
Line of Credit Facility, Collateral		98
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		1.5
Debt Instrument, Covenant, Secondary Current Asset Coverage Ratio		2.1
Bond Tender and Call Premium		$ 0	$ (34,000,000)
Repayments of Long-term Debt, Long-term Capital Lease Obligations, and Capital Securities		15,000,000	$ 440,000,000
364 Day Secured RCF [Member]
Short-term Debt [Line Items]
Short-term debt		317,000,000		$ 317,000,000
Committed letters of credit
Short-term Debt [Line Items]
Letters of Credit Outstanding, Amount		271,000,000
Domestic and foreign facility
Short-term Debt [Line Items]
Short term borrowings		7,000,000
Committed Letters of Credit [Member]
Short-term Debt [Line Items]
Letters of Credit Outstanding, Amount		206,000,000
Revolving Credit Facility
Short-term Debt [Line Items]
Credit agreement, maximum capacity		846,000,000
A&R Credit Agreement
Short-term Debt [Line Items]
Credit agreement, maximum capacity		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
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
Nonextending Lenders [Member] | A&R Credit Agreement
Short-term Debt [Line Items]
Credit agreement, maximum capacity		$ 226,000,000
London Interbank Offered Rate (LIBOR) | Term Loan Agreement
Short-term Debt [Line Items]
Basis spread on variable rate (as a percent)		1.43%
London Interbank Offered Rate (LIBOR) | 364-day credit agreement [Member]
Short-term Debt [Line Items]
Basis spread on variable rate (as a percent)		2.18%
London Interbank Offered Rate (LIBOR) | Extending Lenders | Minimum | A&R Credit Agreement
Short-term Debt [Line Items]
Basis spread on variable rate (as a percent)		2.68%
London Interbank Offered Rate (LIBOR) | Nonextending Lenders [Member] | Minimum | A&R Credit Agreement
Short-term Debt [Line Items]
Basis spread on variable rate (as a percent)		1.93%