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

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Debt (Details) - USD ($) $ in Millions	Jun. 30, 2015	Feb. 24, 2015	Dec. 31, 2014	Jun. 30, 2014	Oct. 31, 2013
Debt Instrument [Line Items]
Debt instrument interest rate				10.00%
Current portion of long-term debt	$ 0		$ 4
Total debt	$ 2,188		$ 2,209
5.5% senior notes due 2025
Debt Instrument [Line Items]
Debt instrument interest rate	5.50%		5.50%
Total debt	$ 350	$ 350	$ 0
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	0		4
Total debt	0		21
Industrial revenue bonds (due 2028 through 2034)
Debt Instrument [Line Items]
Total debt	$ 239		$ 239