Earnings per Share (Unaudited) Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Earnings Per Share [Abstract]
Net income from continuing operations	$ 1,039	$ 326	$ 1,867	$ 594
Net income from continuing operations attributable to noncontrolling interests	(166)	(66)	(291)	(141)
Undistributed earnings allocated to participating securities	(3)	(3)	(4)	(3)
Net income from continuing operations attributable to common stockholders	870	257	1,572	450
Net (loss) income from discontinued operations	(4)	9	(15)	47
Net income from discontinued operations attributable to noncontrolling interests	0	(1)	0	(4)
Net (loss) income from discontinued operations attributable to common stockholders	(4)	8	(15)	43
Net income attributable to common stockholders	$ 866	$ 265	$ 1,557	$ 493
Basic weighted-average shares of common stock outstanding	1,449	1,447	1,449	1,447
Add shares issuable upon exercise or vesting of dilutive stock options and restricted stock units	9	6	9	6
Diluted weighted-average shares of common stock outstanding	1,458	1,453	1,458	1,453
Basic net income (loss) per share attributable to common stockholders:
Income (Loss) from Continuing Operations, Per Basic Share	$ 0.60	$ 0.18	$ 1.08	$ 0.31
Discontinued Operation, Income (Loss) from Discontinued Operation, Net of Tax, Per Basic Share	0.00	0.00	(0.01)	0.03
Earnings Per Share, Basic	0.60	0.18	1.07	0.34
Diluted net income (loss) per share attributable to common stockholders:
Income (Loss) from Continuing Operations, Per Diluted Share	0.59	0.18	1.08	0.31
Discontinued Operation, Income (Loss) from Discontinued Operation, Net of Tax, Per Diluted Share	0.00	0.00	(0.01)	0.03
Earnings Per Share, Diluted	$ 0.59	$ 0.18	$ 1.07	$ 0.34
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	2		3
Dilutive Securities Excluded from Computation of EPS Amount	35	44	34	44