Share-Based Compensation Plans (Details) - USD ($) $ / shares in Units, $ in Millions		12 Months Ended
	Jan. 01, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share Based Compensation Plans
Shares authorized under the plan		55,400,000
Shares available for grant under the plan		14,700,000
General term of awards after they are vested		7 years
Total unrecognized compensation costs related to all unvested share based awards		$ 43
Weighted average period over compensation costs are expected to be recognized		1 year 4 months 24 days
Stock appreciation rights
Equity instruments other than options activity
Granted (in shares)		0	0	0
Outstanding at the end of the period (in shares)	185,002
Vested and exercisable at the end of the period (in shares)		29,288
Weighted-average grant-date fair value per share
Outstanding at the end of the period (in dollars per share)	$ 93.49
Weighted average exercise price per share
Vested and exercisable at the end of the period (in dollars per share)		$ 107.63
Additional disclosure
Aggregate intrinsic value	$ 0
Exercised in period (in shares)		0	0	0
Service-based awards
Share Based Compensation Plans
Vesting period		3 years
Service-based awards | Restricted shares
Equity instruments other than options activity
Outstanding at the beginning of the period (in shares)	3,030,444	3,030,444
Granted (in shares)		3,155,382	2,848,521	1,208,790
Vested (in shares)		(1,725,734)	(1,817,758)	(1,520,023)
Forfeited (in shares)		(454,010)
Outstanding at the end of the period (in shares)		4,006,082	3,030,444
Weighted-average grant-date fair value per share
Outstanding at the beginning of the period (in dollars per share)	$ 25.65	$ 25.65
Granted (in dollars per share)		8.69	$ 18.70	$ 42.80
Vested (in dollars per share)		28.08
Forfeited (in dollars per share)		9.52
Outstanding at the end of the period (in dollars per share)		$ 13.10	$ 25.65
Total grant date fair value		$ 48	$ 81	$ 87
Service-based awards | Stock options
Weighted-average grant-date fair value per share
Granted (in dollars per share)		$ 8.61
Option valuation assumptions
Granted (in dollars per share)		$ 8.61
Dividend yield (as a percent)		0.00%
Expected price volatility (as a percent)		65.00%
Risk free interest rate (as a percent)		1.26%
Expected life of options		6 years 1 month 6 days
Stock option activity
Outstanding at the beginning of the period (in shares)	1,622,317	1,622,317
Granted (in shares)		945,724
Exercised (in shares)			0	(383,848)
Forfeited (in shares)		(633,346)
Outstanding at the end of the period (in shares)		1,934,695	1,622,317
Vested and exercisable at the end of the period (in shares)		1,022,393
Weighted-average exercise price per share
Outstanding at the beginning of the period (in dollars per share)	$ 73.66	$ 73.66
Granted (in dollars per share)		8.61
Forfeited (in dollars per share)		64.44
Outstanding at the end of the period (in dollars per share)		44.88	$ 73.66
Vested and exercisable at the end of the period (in dollars per share)		$ 77.24
Weighted-average remaining contractual term
Outstanding		6 years 1 month 13 days	4 years 9 months 22 days
Vested and exercisable at the end of the period		3 years 5 months 12 days
Aggregate intrinsic value (in millions)
Aggregate intrinsic value		$ 6	$ 0
Additional disclosure
Total grant-date fair value of awards vested		$ 3	$ 9	$ 14
Intrinsic value exercised during the period				$ 2
Unvested stock options outstanding (in shares)		912,302
Performance-based awards
Share Based Compensation Plans
Vesting period		1 year
Measurement period		3 years
Performance-based awards | Restricted shares
Equity instruments other than options activity
Outstanding at the beginning of the period (in shares)	702,131	702,131
Granted (in shares)		997,362	652,592	302,630
Vested (in shares)		(187,000)	0
Forfeited (in shares)		(72,887)
Outstanding at the end of the period (in shares)		1,439,606	702,131
Weighted-average grant-date fair value per share
Outstanding at the beginning of the period (in dollars per share)	$ 18.81	$ 18.81
Granted (in dollars per share)		11.60	$ 17.91	$ 31.73
Vested (in dollars per share)		32.05
Forfeited (in dollars per share)		17.12
Outstanding at the end of the period (in dollars per share)		$ 14.40	$ 18.81
Total grant date fair value		$ 6		$ 8
Performance-based awards | Stock options
Stock option activity
Exercised (in shares)		0	0	(12,073)
Outstanding at the end of the period (in shares)	150,360
Weighted-average exercise price per share
Outstanding at the end of the period (in dollars per share)	$ 82.50
Aggregate intrinsic value (in millions)
Aggregate intrinsic value	$ 0
Maximum | Stock appreciation rights
Share Based Compensation Plans
General term of awards after they are vested	1 year
Weighted-average remaining contractual term
Vested and exercisable, at the end of the period		1 year
Maximum | Performance-based awards | Stock options
Share Based Compensation Plans
General term of awards after they are vested	1 year