Debt (Tables)

12 Months Ended

Dec. 31, 2015

Debt Disclosure [Abstract]

Schedule of total debt

Total debt as of December 31 consisted of the following:

(millions)	2015		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	500		500
7.875% senior notes due 2020 (net of discount: 2015 - $1; 2014 - $1)	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
Less unamortized debt issuance costs (a)	$	13	$	14
Total	$	2,175	$	2,195

(a) Reflects the change in presentation of unamortized debt issuance costs from other assets to a reduction in debt. See Note 2.

The indentures governing the notes contain events of default, covenants and restrictions that are customary for similar transactions, including a limitation on our ability and the ability of certain of our subsidiaries to create or incur secured indebtedness.

Interest rate (a)	6.30%	7.75%	5.500%	7.875%	5.875%
Principal net of discount (in millions) (b)	$500	$500	$350	$249	$350
Maturity	November 15, 2016	January 15, 2018	March 1, 2025	March 30, 2020	November 1, 2021
Call date	Any time (c)	Any time (c)	March 1, 2020 (d)	March 30, 2016 (d)	November 1, 2016 (d)
Mandatory redemption	at 101% plus accrued and unpaid interest in the event of a change in control and a related downgrade below investment grade by both Moody’s Investors Service and Standard & Poor’s Financial Services LLC		at 101% plus accrued and unpaid interest in the event of a change in control

(a) The 7.75% senior notes currently have an effective interest rate of 9.75%. The rate is subject to an adjustment of up to 2% if the debt rating is downgraded or subsequently upgraded by Moody's Investors Service and Standard & Poor's Financial Services LLC.

(b) Principal amounts do not include unamortized debt issuance costs that have been reclassified from other assets to a reduction in debt. See Note 2.

(c) Callable at any time at a price equal to the greater of (1) 100% of the principal and (2) the sum of the present value of the remaining scheduled payments of principal and interest discounted to the redemption date on a semi-annual basis at the applicable U.S. Treasury rate plus a spread (as outlined in the respective indentures), plus any accrued and unpaid interest on the principal amount being called.

(d) Callable at any time prior to the call date at a price equal to 100% of the principal plus a premium (as outlined in the respective indentures), plus any accrued and unpaid interest on the principal amount being called. Callable after the call date at stated redemption prices (as outlined in the respective indentures), plus any accrued and unpaid interest on the principal amount being called.

Schedule of amounts of total debt outstanding maturing in each of next five years and beyond

As of December 31, 2015, the amounts of total debt outstanding maturing in each of the next five years and beyond were as follows:

(millions)	2016		2017		2018		2019		2020		After 2020
Debt maturities (principal amounts)	$	500	$	—	$	500	$	—	$	250	$	939