Contractual interest rate for funds borrowed, under the debt agreement.

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The amount of debt discount that was originally recognized at the issuance of the instrument that has yet to be amortized.

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Carrying amount of long-term debt, net of unamortized discount or premium, including current and noncurrent amounts. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Debt - Total Debt (Details) - USD ($) $ in Millions	Dec. 31, 2015	Feb. 24, 2015	Dec. 31, 2014	Oct. 31, 2013
Debt Instrument [Line Items]
Long-term debt	$ 2,188		$ 2,209
Less unamortized debt issuance costs	13		14
Total	2,175		2,195
Current portion of long-term debt	500		4
5.5% senior notes due 2025
Debt Instrument [Line Items]
Long-term debt	350		$ 0
Less unamortized debt issuance costs		$ 6
Total	$ 344
Stated interest rate	5.50%		5.50%
5.875% senior notes due 2021
Debt Instrument [Line Items]
Long-term debt	$ 350		$ 350	$ 350
Stated interest rate	5.875%		5.875%	5.875%
6.3% senior notes due 2016
Debt Instrument [Line Items]
Long-term debt	$ 500		$ 500
Stated interest rate	6.30%		6.30%
7.75% senior notes due 2018
Debt Instrument [Line Items]
Long-term debt	$ 500		$ 500
Stated interest rate	7.75%		7.75%
7.875% senior notes due 2020 (net of discount: 2015 - $1; 2014 - $1)
Debt Instrument [Line Items]
Long-term debt	$ 249		$ 249
Stated interest rate	7.875%		7.875%
Unamortized discount	$ 1		$ 1
8.375% senior notes due 2018
Debt Instrument [Line Items]
Long-term debt	$ 0		$ 350
Stated interest rate	8.375%		8.375%
Ship mortgage facility (includes current portion of long-term debt: 2015 - $0; 2014 - $4)
Debt Instrument [Line Items]
Long-term debt	$ 0		$ 21
Current portion of long-term debt	0		4
Industrial revenue bonds (due 2028 through 2034)
Debt Instrument [Line Items]
Long-term debt	$ 239		$ 239