Debt (Tables)

6 Months Ended

Jun. 30, 2015

Debt Disclosure [Abstract]

Schedule of long-term debt instruments

Total debt, including the current portion of long-term debt, consisted of the following:

(millions)	June 30, 2015		December 31, 2014
5.5% senior notes due 2025	$	350	$	—
5.875% senior notes due 2021	350		350
6.3% senior notes due 2016	500		500
7.75% senior notes due 2018, net of discount	500		500
7.875% senior notes due 2020, net of discount	249		249
8.375% senior notes due 2018	—		350
Ship mortgage facility (includes current portion of long-term debt: 2015 - $0, 2014 - $4)	—		21
Industrial revenue bonds (due 2028 through 2034)	239		239
Total	$	2,188	$	2,209