Earnings per Share (Unaudited) Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Earnings Per Share [Abstract]
Net income (loss) from continuing operations	$ 268	$ (4,097)
Net income from continuing operations attributable to noncontrolling interests	75	62
Preferred dividends on redeemable noncontrolling interest	0	11
Undistributed earnings allocated to participating securities	3	3
Net income (loss) from continuing operations attributable to common stockholders	190	(4,173)
Net income (loss) from discontinued operations	38	(4)
Net income from discontinued operations attributable to noncontrolling interests	3	10
Net income (loss) from discontinued operations attributable to common stockholders	35	(14)
Net income (loss) attributable to common stockholders	$ 225	$ (4,187)
Add shares issuable upon exercise or vesting of dilutive stock options and restricted stock units	8	0
Diluted weighted-average shares of common stock outstanding	1,454	1,251
Basic and diluted net income (loss) per share attributable to common stockholders
Continuing operations	$ 0.13	$ (3.34)
Discontinued operations	0.03	(0.01)
Basic and diluted net income (loss) per share attributable to common stockholders:	$ 0.16	$ (3.35)
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount		10
Dilutive Securities Excluded from Computation of EPS Amount	44	47