Earnings per Share (Unaudited) Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Earnings Per Share [Abstract]
Net income (loss) from continuing operations	$ 953	$ (549)
Undistributed earnings allocated to participating securities	(4)	(3)
Net income (loss) attributable to common stockholders	$ 714	$ (494)
Basic weighted-average shares of common stock outstanding	1,462	1,452
Add shares issuable upon exercise or vesting of dilutive stock options and restricted stock units (RSUs)	15	0
Diluted weighted-average shares of common stock outstanding	1,477	1,452
Basic and diluted net income (loss) per share attributable to common stockholders:
Earnings per share, basic (in dollars per share)	$ 0.49	$ (0.34)
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount		10
Dilutive Securities Excluded from Computation of EPS Amount	10	40