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

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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 (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014	Feb. 24, 2015	Oct. 31, 2013
Debt Instrument [Line Items]
Current portion of long-term debt	$ 4us-gaap_LongTermDebtCurrent	$ 4us-gaap_LongTermDebtCurrent
Total debt	2,206us-gaap_LongTermDebt	2,209us-gaap_LongTermDebt
5.5% senior notes due 2025
Debt Instrument [Line Items]
Debt instrument interest rate	5.50%	5.50%
Total debt	350	0	350
5.875% senior notes due 2021
Debt Instrument [Line Items]
Debt instrument interest rate	5.875%	5.875%
Total debt	350	350		350
6.3% senior notes due 2016
Debt Instrument [Line Items]
Debt instrument interest rate	6.30%	6.30%
Total debt	500	500
7.75% senior notes due 2018, net of discount
Debt Instrument [Line Items]
Debt instrument interest rate	7.75%	7.75%
Total debt	500	500
7.875% senior notes due 2020, net of discount
Debt Instrument [Line Items]
Debt instrument interest rate	7.875%	7.875%
Total debt	249	249
8.375% senior notes due 2018
Debt Instrument [Line Items]
Debt instrument interest rate	8.375%	8.375%
Total debt	0	350
Ship mortgage facility
Debt Instrument [Line Items]
Current portion of long-term debt	4	4
Total debt	18	21
Industrial revenue bonds (due 2028 through 2034)
Debt Instrument [Line Items]
Total debt	$ 239	$ 239