Net Income (loss) Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Numerator:
Income (loss) from continuing operations	$ 545	$ 509	$ 1,424	$ (1,594)
Income (loss) from discontinued operations, net of income taxes	(6)	164	(176)	617
Net income (loss)	$ 539	$ 673	$ 1,248	$ (977)
Denominator:
Weighted average shares of common stock - basic	1,210	1,242	1,214	1,258
Dilutive effect of equity incentive awards (in shares)	13	9	12	0
Weighted average shares of common stock - diluted	1,223	1,251	1,226	1,258
Income (loss) per share - basic:
Continuing operations (in usd per share)	$ 0.45	$ 0.41	$ 1.17	$ (1.27)
Discontinued operations (in usd per share)	0.00	0.13	(0.14)	0.49
Net income (loss) per share - basic (usd per share)	0.45	0.54	1.03	(0.78)
Income (loss) per share - diluted:
Continuing operations (in usd per share)	0.45	0.41	1.16	(1.27)
Discontinued operations (in usd per share)	0.00	0.13	(0.14)	0.49
Net income (loss) per share - diluted (in usd per share)	$ 0.45	$ 0.54	$ 1.02	$ (0.78)
Common stock equivalents excluded from income per diluted share because their effect would have been anti-dilutive (in shares)	4	8	2	54