Consolidated Statements of Shareholders' Equity - USD ($) $ in Millions	Total	Common Stock	Additional Paid in Capital	Accumulated Other Comprehensive Loss	Treasury Stock at Cost	Retained Earnings
Balance at Beginning of Period at Dec. 31, 2014	$ 10,325	$ 4	$ 3,624	$ (90)	$ (671)	$ 7,458
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Loss	(131)	0	0	0	0	(131)
Stock-based Compensation	38	0	38	0	0	0
Dividends	(134)	0	0	0	0	(134)
Issuance of Shares of Common Stock to Public, Net of Offering Costs	1,112	0	1,112	0	0	0
Other	(1)	0	4	7	(12)	0
Balance at End of Period at Jun. 30, 2015	11,209	4	4,778	(83)	(683)	7,193
Balance at Beginning of Period at Dec. 31, 2015	10,370	5	6,360	(33)	(688)	4,726
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Loss	(602)	0	0	0	0	(602)
Stock-based Compensation	36	0	36	0	0	0
Dividends	(86)	0	0	0	0	(86)
Other	(5)	0	2	1	(8)	0
Balance at End of Period at Jun. 30, 2016	$ 9,713	$ 5	$ 6,398	$ (32)	$ (696)	$ 4,038