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
Shareholders Equity, Beginning Balance at Dec. 31, 2012	$ 8,258	$ 4	$ 3,302	$ (113)	$ (648)	$ 5,713
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income (Loss)	978	0	0	0	0	978
Stock-based Compensation	80	0	80	0	0	0
Exercise of Stock Options	51	0	51	0	0	0
Tax Benefits Related to Exercise of Stock Options	20	0	20	0	0	0
Dividends	(198)	0	0	0	0	(198)
Changes in Treasury Stock, Net	(14)	0	0	0	(14)	0
Rabbi Trust Shares Sold	13	0	10	0	3	0
Net Change in Pension and Other	(4)	0	0	(4)	0	0
Shareholders Equity, Ending Balance at Dec. 31, 2013	9,184	4	3,463	(117)	(659)	6,493
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income (Loss)	1,214	0	0	0	0	1,214
Stock-based Compensation	87	0	87	0	0	0
Exercise of Stock Options	48	0	48	0	0	0
Tax Benefits Related to Exercise of Stock Options	19	0	19	0	0	0
Dividends	(249)	0	0	0	0	(249)
Changes in Treasury Stock, Net	(16)	0	0	0	(16)	0
Rabbi Trust Shares Sold	11	0	7	0	4	0
Net Change in Pension and Other	27	0	0	27	0	0
Shareholders Equity, Ending Balance at Dec. 31, 2014	10,325	4	3,624	(90)	(671)	7,458
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income (Loss)	(2,441)	0	0	0	0	(2,441)
Rosetta Merger	1,529	1	1,528	0	0	0
Stock-based Compensation	86	0	86	0	0	0
Exercise of Stock Options	8	0	8	0	0	0
Tax Benefits Related to Exercise of Stock Options	(1)	0	(1)	0	0	0
Dividends	(291)	0	0	0	0	(291)
Changes in Treasury Stock, Net	(21)	0	0	0	(21)	0
Rabbi Trust Shares Sold	7	0	3	0	4	0
Issuance of Shares of Common Stock to Public, Net of Offering Costs	1,112	0	1,112	0	0	0
Net Change in Pension and Other	57	0	0	57	0	0
Shareholders Equity, Ending Balance at Dec. 31, 2015	$ 10,370	$ 5	$ 6,360	$ (33)	$ (688)	$ 4,726